diff --git a/Cargo.lock b/Cargo.lock
index 071803b3..2d6d2cec 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,7 +2,7 @@
 # It is not intended for manual editing.
 [[package]]
 name = "addr2line"
-version = "0.12.0"
+version = "0.12.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "gimli 0.21.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -92,9 +92,9 @@ name = "async-trait"
 version = "0.1.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -102,7 +102,7 @@ name = "atty"
 version = "0.2.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "hermit-abi 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "hermit-abi 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.70 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -117,7 +117,7 @@ name = "backtrace"
 version = "0.3.48"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "addr2line 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "addr2line 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.70 (registry+https://github.com/rust-lang/crates.io-index)",
  "object 0.19.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -328,9 +328,9 @@ version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -441,9 +441,9 @@ version = "0.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro-hack 0.5.15 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -471,7 +471,7 @@ dependencies = [
  "futures-sink 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures-task 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "memchr 2.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "pin-utils 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "proc-macro-hack 0.5.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "proc-macro-nested 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -529,7 +529,7 @@ dependencies = [
 
 [[package]]
 name = "hermit-abi"
-version = "0.1.12"
+version = "0.1.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "libc 0.2.70 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -603,7 +603,7 @@ dependencies = [
  "itoa 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "net2 0.2.34 (registry+https://github.com/rust-lang/crates.io-index)",
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-service 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -921,7 +921,7 @@ name = "num_cpus"
 version = "1.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "hermit-abi 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "hermit-abi 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.70 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1008,9 +1008,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "pest 2.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "pest_meta 2.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1025,20 +1025,20 @@ dependencies = [
 
 [[package]]
 name = "pin-project"
-version = "0.4.16"
+version = "0.4.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "pin-project-internal 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project-internal 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "pin-project-internal"
-version = "0.4.16"
+version = "0.4.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1068,7 +1068,7 @@ dependencies = [
 
 [[package]]
 name = "ppv-lite86"
-version = "0.2.6"
+version = "0.2.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -1083,7 +1083,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.12"
+version = "1.0.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1104,10 +1104,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "quote"
-version = "1.0.5"
+version = "1.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1127,7 +1127,7 @@ name = "rand_chacha"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "ppv-lite86 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ppv-lite86 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1289,9 +1289,9 @@ name = "serde_derive"
 version = "1.0.110"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1361,7 +1361,7 @@ dependencies = [
  "native-tls 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "nix 0.17.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl 0.10.29 (registry+https://github.com/rust-lang/crates.io-index)",
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "qrcode 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1377,7 +1377,7 @@ dependencies = [
  "strum_macros 0.18.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-native-tls 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio-rustls 0.13.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-rustls 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "trust-dns-proto 0.19.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "trust-dns-resolver 0.19.5 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1451,9 +1451,9 @@ version = "0.18.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1463,11 +1463,11 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "syn"
-version = "1.0.21"
+version = "1.0.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1528,20 +1528,20 @@ dependencies = [
 
 [[package]]
 name = "thiserror"
-version = "1.0.17"
+version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "thiserror-impl 1.0.17 (registry+https://github.com/rust-lang/crates.io-index)",
+ "thiserror-impl 1.0.18 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "thiserror-impl"
-version = "1.0.17"
+version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1589,9 +1589,9 @@ name = "tokio-macros"
 version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1605,7 +1605,7 @@ dependencies = [
 
 [[package]]
 name = "tokio-rustls"
-version = "0.13.0"
+version = "0.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures-core 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1650,7 +1650,7 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures-core 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-layer 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-service 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1663,7 +1663,7 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures-core 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-service 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1678,7 +1678,7 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures-core 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-layer 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-load 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1692,7 +1692,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures-core 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-discover 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-service 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1704,7 +1704,7 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures-core 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-layer 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-service 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1715,7 +1715,7 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures-core 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-layer 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-service 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1731,7 +1731,7 @@ name = "tower-timeout"
 version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-layer 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-service 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1744,7 +1744,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "futures-core 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures-util 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-service 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1764,9 +1764,9 @@ name = "tracing-attributes"
 version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1790,9 +1790,9 @@ dependencies = [
  "http 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustls 0.17.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "thiserror 1.0.17 (registry+https://github.com/rust-lang/crates.io-index)",
+ "thiserror 1.0.18 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio-rustls 0.13.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-rustls 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "trust-dns-proto 0.19.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "trust-dns-rustls 0.19.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "typed-headers 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1814,7 +1814,7 @@ dependencies = [
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "thiserror 1.0.17 (registry+https://github.com/rust-lang/crates.io-index)",
+ "thiserror 1.0.18 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1834,9 +1834,9 @@ dependencies = [
  "resolv-conf 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustls 0.17.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "thiserror 1.0.17 (registry+https://github.com/rust-lang/crates.io-index)",
+ "thiserror 1.0.18 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio-rustls 0.13.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-rustls 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "trust-dns-https 0.19.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "trust-dns-proto 0.19.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "trust-dns-rustls 0.19.5 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1852,7 +1852,7 @@ dependencies = [
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustls 0.17.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio-rustls 0.13.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-rustls 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "trust-dns-proto 0.19.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "webpki 0.21.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1976,9 +1976,9 @@ dependencies = [
  "bumpalo 3.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen-shared 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1987,7 +1987,7 @@ name = "wasm-bindgen-macro"
 version = "0.2.62"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen-macro-support 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1996,9 +1996,9 @@ name = "wasm-bindgen-macro-support"
 version = "0.2.62"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen-backend 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen-shared 0.2.62 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -2107,7 +2107,7 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [metadata]
-"checksum addr2line 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)" = "456d75cbb82da1ad150c8a9d97285ffcd21c9931dcb11e995903e7d75141b38b"
+"checksum addr2line 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)" = "a49806b9dadc843c61e7c97e72490ad7f7220ae249012fbda9ad0609457c0543"
 "checksum adler32 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "5d2e7343e7fc9de883d1b0341e0b13970f764c14101234857d2ddafa1cb1cac2"
 "checksum aead 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "4cf01b9b56e767bb57b94ebf91a58b338002963785cdd7013e21c0d4679471e4"
 "checksum aes 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "54eb1d8fe354e5fc611daf4f2ea97dd45a765f4f1e4512306ec183ae2e8f20c9"
@@ -2172,7 +2172,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum gimli 0.21.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bcc8e0c9bce37868955864dbecd2b1ab2bdf967e6f28066d65aaac620444b65c"
 "checksum h2 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)" = "79b7246d7e4b979c03fa093da39cfb3617a96bbeee6310af63991668d7e843ff"
 "checksum heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "20564e78d53d2bb135c343b3f47714a56af2061f1c928fdb541dc7b9fdd94205"
-"checksum hermit-abi 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)" = "61565ff7aaace3525556587bd2dc31d4a07071957be715e63ce7b1eccf51a8f4"
+"checksum hermit-abi 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)" = "91780f809e750b0a89f5544be56617ff6b1227ee485bcb06ebe10cdf89bd3b71"
 "checksum hkdf 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3fa08a006102488bd9cd5b8013aabe84955cf5ae22e304c2caf655b633aefae3"
 "checksum hmac 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "5dcb5e64cda4c23119ab41ba960d1e170a774c8e4b9d9e6a9bc18aabf5e59695"
 "checksum hostname 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3c731c3e10504cc8ed35cfe2f1db4c9274c3d35fa486e3b31df46f068ef3e867"
@@ -2228,19 +2228,19 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum pest_derive 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "833d1ae558dc601e9a60366421196a8d94bc0ac980476d0b67e1d0988d72b2d0"
 "checksum pest_generator 2.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "99b8db626e31e5b81787b9783425769681b347011cc59471e33ea46d2ea0cf55"
 "checksum pest_meta 2.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "54be6e404f5317079812fc8f9f5279de376d8856929e21c184ecf6bbd692a11d"
-"checksum pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)" = "81d480cb4e89522ccda96d0eed9af94180b7a5f93fb28f66e1fd7d68431663d1"
-"checksum pin-project-internal 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)" = "a82996f11efccb19b685b14b5df818de31c1edcee3daa256ab5775dd98e72feb"
+"checksum pin-project 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)" = "edc93aeee735e60ecb40cf740eb319ff23eab1c5748abfdb5c180e4ce49f7791"
+"checksum pin-project-internal 0.4.17 (registry+https://github.com/rust-lang/crates.io-index)" = "e58db2081ba5b4c93bd6be09c40fd36cb9193a8336c384f3b40012e531aa7e40"
 "checksum pin-project-lite 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "f7505eeebd78492e0f6108f7171c4948dbb120ee8119d9d77d0afa5469bef67f"
 "checksum pin-utils 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 "checksum pkg-config 0.3.17 (registry+https://github.com/rust-lang/crates.io-index)" = "05da548ad6865900e60eaba7f589cc0783590a92e940c26953ff81ddbab2d677"
 "checksum pmac 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bd76d63e86aa67a4bd063079f0d93bb8730b036eea5697345f651e6874ea61e5"
-"checksum ppv-lite86 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)" = "74490b50b9fbe561ac330df47c08f3f33073d2d00c150f719147d7c54522fa1b"
+"checksum ppv-lite86 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)" = "237a5ed80e274dbc66f86bd59c1e25edc039660be53194b5fe0a482e0f2612ea"
 "checksum proc-macro-hack 0.5.15 (registry+https://github.com/rust-lang/crates.io-index)" = "0d659fe7c6d27f25e9d80a1a094c223f5246f6a6596453e09d7229bf42750b63"
 "checksum proc-macro-nested 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "8e946095f9d3ed29ec38de908c22f95d9ac008e424c7bcae54c75a79c527c694"
-"checksum proc-macro2 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)" = "8872cf6f48eee44265156c111456a700ab3483686b3f96df4cf5481c89157319"
+"checksum proc-macro2 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)" = "53f5ffe53a6b28e37c9c1ce74893477864d64f74778a93a4beb43c8fa167f639"
 "checksum qrcode 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)" = "16d2f1455f3630c6e5107b4f2b94e74d76dea80736de0981fd27644216cff57f"
 "checksum quick-error 1.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "a1d01941d82fa2ab50be1e79e6714289dd7cde78eba4c074bc5a4374f650dfe0"
-"checksum quote 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "42934bc9c8ab0d3b273a16d8551c8f0fcff46be73276ca083ec2414c15c4ba5e"
+"checksum quote 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)" = "54a21852a652ad6f610c9510194f398ff6f8692e334fd1145fed931f7fbe44ea"
 "checksum rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)" = "6a6b1679d49b24bbfe0c803429aa1874472f50d9b363131f0e89fc356b544d03"
 "checksum rand_chacha 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f4c8ed856279c9737206bf725bf36935d8666ead7aa69b52be55af369d193402"
 "checksum rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "90bde5296fc891b0cef12a6d03ddccc162ce7b2aff54160af9338f8d40df6d19"
@@ -2276,21 +2276,21 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum strum 0.18.0 (registry+https://github.com/rust-lang/crates.io-index)" = "57bd81eb48f4c437cadc685403cad539345bf703d78e63707418431cecd4522b"
 "checksum strum_macros 0.18.0 (registry+https://github.com/rust-lang/crates.io-index)" = "87c85aa3f8ea653bfd3ddf25f7ee357ee4d204731f6aa9ad04002306f6e2774c"
 "checksum subtle 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "2d67a5a62ba6e01cb2192ff309324cb4875d0c451d55fe2319433abe7a05a8ee"
-"checksum syn 1.0.21 (registry+https://github.com/rust-lang/crates.io-index)" = "4696caa4048ac7ce2bcd2e484b3cef88c1004e41b8e945a277e2c25dc0b72060"
+"checksum syn 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)" = "1425de3c33b0941002740a420b1a906a350b88d08b82b2c8a01035a3f9447bac"
 "checksum take_mut 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f764005d11ee5f36500a149ace24e00e3da98b0158b3e2d53a7495660d3f4d60"
 "checksum tar 0.4.26 (registry+https://github.com/rust-lang/crates.io-index)" = "b3196bfbffbba3e57481b6ea32249fbaf590396a52505a2615adbb79d9d826d3"
 "checksum tempfile 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e24d9338a0a5be79593e2fa15a648add6138caa803e2d5bc782c371732ca9"
 "checksum term_size 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1e4129646ca0ed8f45d09b929036bafad5377103edd06e50bf574b353d2b08d9"
 "checksum termcolor 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bb6bfa289a4d7c5766392812c0a1f4c1ba45afa1ad47803c11e1f407d846d75f"
 "checksum textwrap 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d326610f408c7a4eb6f51c37c330e496b08506c9457c9d34287ecc38809fb060"
-"checksum thiserror 1.0.17 (registry+https://github.com/rust-lang/crates.io-index)" = "467e5ff447618a916519a4e0d62772ab14f434897f3d63f05d8700ef1e9b22c1"
-"checksum thiserror-impl 1.0.17 (registry+https://github.com/rust-lang/crates.io-index)" = "e63c1091225b9834089b429bc4a2e01223470e3183e891582909e9d1c4cb55d9"
+"checksum thiserror 1.0.18 (registry+https://github.com/rust-lang/crates.io-index)" = "5976891d6950b4f68477850b5b9e5aa64d955961466f9e174363f573e54e8ca7"
+"checksum thiserror-impl 1.0.18 (registry+https://github.com/rust-lang/crates.io-index)" = "ab81dbd1cd69cd2ce22ecfbdd3bdb73334ba25350649408cc6c085f46d89573d"
 "checksum thread_local 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "d40c6d1b69745a6ec6fb1ca717914848da4b44ae29d9b3080cbee91d72a69b14"
 "checksum time 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)" = "ca8a50ef2360fbd1eeb0ecd46795a87a19024eb4b53c5dc916ca1fd95fe62438"
 "checksum tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)" = "d099fa27b9702bed751524694adbe393e18b36b204da91eb1cbbbbb4a5ee2d58"
 "checksum tokio-macros 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)" = "f0c3acc6aa564495a0f2e1d59fab677cd7f81a19994cfc7f3ad0e64301560389"
 "checksum tokio-native-tls 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "cd608593a919a8e05a7d1fc6df885e40f6a88d3a70a3a7eff23ff27964eda069"
-"checksum tokio-rustls 0.13.0 (registry+https://github.com/rust-lang/crates.io-index)" = "4adb8b3e5f86b707f1b54e7c15b6de52617a823608ccda98a15d3a24222f265a"
+"checksum tokio-rustls 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)" = "15cb62a0d2770787abc96e99c1cd98fcf17f94959f3af63ca85bdfb203f051b4"
 "checksum tokio-util 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "be8242891f2b6cbef26a2d7e8605133c2c554cd35b3e4948ea892d6d68436499"
 "checksum tower 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "fd3169017c090b7a28fce80abaad0ab4f5566423677c9331bb320af7e49cfe62"
 "checksum tower-buffer 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "c4887dc2a65d464c8b9b66e0e4d51c2fd6cf5b3373afc72805b0a60bce00446a"
diff --git a/Cargo.toml b/Cargo.toml
index 4d8d213c..4727817f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,7 +41,7 @@ incremental = false
 panic = "abort"
 
 [features]
-default = ["sodium", "rc4", "aes-cfb", "aes-ctr", "trust-dns", "local-http", "local-tunnel", "local-http-native-tls"]
+default = ["sodium", "rc4", "aes-cfb", "aes-ctr", "trust-dns", "local-http", "local-http-native-tls", "local-tunnel", "local-socks4"]
 # Enables ciphers that depending on libsodium
 # chacha20, xchacha20, chacha20-ietf
 # salsa20, xsalsa20
@@ -77,6 +77,8 @@ local-http-rustls = ["tokio-rustls", "webpki-roots", "rustls-native-certs"]
 local-redir = []
 # Enable tunnel protocol for sslocal
 local-tunnel = []
+# Enable SOCKS4/4a protocol for sslocal
+local-socks4 = []
 
 [dependencies]
 log = "0.4"
diff --git a/src/bin/local.rs b/src/bin/local.rs
index 6baad13c..e29e5058 100644
--- a/src/bin/local.rs
+++ b/src/bin/local.rs
@@ -30,6 +30,8 @@ mod validator;
 
 const AVAILABLE_PROTOCOLS: &[&str] = &[
     "socks5",
+    #[cfg(feature = "local-socks4")]
+    "socks4",
     #[cfg(feature = "local-http")]
     "http",
     #[cfg(feature = "local-tunnel")]
@@ -128,6 +130,8 @@ fn main() {
 
     let config_type = match matches.value_of("PROTOCOL") {
         Some("socks5") => ConfigType::Socks5Local,
+        #[cfg(feature = "local-socks4")]
+        Some("socks4") => ConfigType::Socks4Local,
         #[cfg(feature = "local-http")]
         Some("http") => ConfigType::HttpLocal,
         #[cfg(feature = "local-tunnel")]
diff --git a/src/config.rs b/src/config.rs
index e4019c2f..2ae00fd1 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -583,6 +583,12 @@ pub enum ConfigType {
     /// Requires `local` configuration
     Socks5Local,
 
+    /// Config for socks4 local
+    ///
+    /// Requires `local` configuration
+    #[cfg(feature = "local-socks4")]
+    Socks4Local,
+
     /// Config for HTTP local
     ///
     /// Requires `local` configuration
@@ -619,6 +625,8 @@ impl ConfigType {
     pub fn is_local(self) -> bool {
         match self {
             ConfigType::Socks5Local => true,
+            #[cfg(feature = "local-socks4")]
+            ConfigType::Socks4Local => true,
             #[cfg(feature = "local-dns-relay")]
             ConfigType::DnsLocal => true,
             #[cfg(feature = "local-tunnel")]
@@ -635,6 +643,8 @@ impl ConfigType {
     pub fn is_server(self) -> bool {
         match self {
             ConfigType::Socks5Local => false,
+            #[cfg(feature = "local-socks4")]
+            ConfigType::Socks4Local => false,
             #[cfg(feature = "local-dns-relay")]
             ConfigType::DnsLocal => false,
             #[cfg(feature = "local-tunnel")]
diff --git a/src/relay/local.rs b/src/relay/local.rs
index dfdf7d90..793d65a2 100644
--- a/src/relay/local.rs
+++ b/src/relay/local.rs
@@ -47,18 +47,25 @@ pub async fn run(mut config: Config) -> io::Result<()> {
     let mut vf = Vec::new();
 
     let enable_tcp = match config_type {
-        #[cfg(not(target_os = "android"))]
         // Socks5 always true, because UDP associate command also requires a TCP connection
+        #[cfg(not(target_os = "android"))]
         ConfigType::Socks5Local => true,
         // On Android, we allows UDP only mode to support fallback UDP upstream
         #[cfg(target_os = "android")]
         ConfigType::Socks5Local => mode.enable_tcp(),
+
+        // Socks4 always true
+        #[cfg(feature = "local-socks4")]
+        ConfigType::Socks4Local => true,
+
         // Tunnel mode controlled by this flag
         #[cfg(feature = "local-tunnel")]
         ConfigType::TunnelLocal => mode.enable_tcp(),
+
         // HTTP must be TCP
         #[cfg(feature = "local-http")]
         ConfigType::HttpLocal => true,
+
         // Redir mode controlled by this flag
         #[cfg(feature = "local-redir")]
         ConfigType::RedirLocal => mode.enable_tcp(),
diff --git a/src/relay/mod.rs b/src/relay/mod.rs
index e941381a..6f9165bc 100644
--- a/src/relay/mod.rs
+++ b/src/relay/mod.rs
@@ -10,6 +10,7 @@ pub mod manager;
 #[cfg(feature = "local-redir")]
 pub(crate) mod redir;
 pub mod server;
+pub mod socks4;
 pub mod socks5;
 pub(crate) mod sys;
 pub mod tcprelay;
diff --git a/src/relay/socks4.rs b/src/relay/socks4.rs
new file mode 100644
index 00000000..45b247bf
--- /dev/null
+++ b/src/relay/socks4.rs
@@ -0,0 +1,375 @@
+//! Socks4a Protocol Definition
+//!
+//! http://ftp.icm.edu.pl/packages/socks/socks4/SOCKS4.protocol
+
+use std::{
+    fmt,
+    io::{self, Error, ErrorKind},
+    net::{Ipv4Addr, SocketAddr, SocketAddrV4},
+};
+
+use byteorder::{BigEndian, ByteOrder};
+use bytes::{BufMut, BytesMut};
+use tokio::io::{AsyncBufRead, AsyncBufReadExt, AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
+
+use crate::relay::socks5;
+
+#[rustfmt::skip]
+mod consts {
+    pub const SOCKS4_VERSION:                                  u8 = 4;
+
+    pub const SOCKS4_COMMAND_CONNECT:                          u8 = 1;
+    pub const SOCKS4_COMMAND_BIND:                             u8 = 2;
+
+    pub const SOCKS4_RESULT_REQUEST_GRANTED:                   u8 = 90;
+    pub const SOCKS4_RESULT_REQUEST_REJECTED_OR_FAILED:        u8 = 91;
+    pub const SOCKS4_RESULT_REQUEST_REJECTED_CANNOT_CONNECT:   u8 = 92;
+    pub const SOCKS4_RESULT_REQUEST_REJECTED_DFFERENT_USER_ID: u8 = 93;
+}
+
+/// SOCKS4 Command
+#[derive(Clone, Debug, Copy)]
+pub enum Command {
+    /// CONNECT command
+    Connect,
+    /// BIND command
+    Bind,
+}
+
+impl Command {
+    #[inline]
+    fn as_u8(self) -> u8 {
+        match self {
+            Command::Connect => consts::SOCKS4_COMMAND_CONNECT,
+            Command::Bind => consts::SOCKS4_COMMAND_BIND,
+        }
+    }
+
+    #[inline]
+    fn from_u8(code: u8) -> Option<Command> {
+        match code {
+            consts::SOCKS4_COMMAND_CONNECT => Some(Command::Connect),
+            consts::SOCKS4_COMMAND_BIND => Some(Command::Bind),
+            _ => None,
+        }
+    }
+}
+
+/// SOCKS4 Result Code
+#[derive(Clone, Debug, Copy)]
+pub enum ResultCode {
+    /// 90: request granted
+    RequestGranted,
+    /// 91: request rejected or failed
+    RequestRejectedOrFailed,
+    /// 92: request rejected becasue SOCKS server cannot connect to identd on the client
+    RequestRejectedCannotConnect,
+    /// 93: request rejected because the client program and identd report different user-ids
+    RequestRejectedDifferentUserId,
+    /// Other replies
+    Other(u8),
+}
+
+impl ResultCode {
+    #[inline]
+    fn as_u8(self) -> u8 {
+        match self {
+            ResultCode::RequestGranted => consts::SOCKS4_RESULT_REQUEST_GRANTED,
+            ResultCode::RequestRejectedOrFailed => consts::SOCKS4_RESULT_REQUEST_REJECTED_OR_FAILED,
+            ResultCode::RequestRejectedCannotConnect => consts::SOCKS4_RESULT_REQUEST_REJECTED_CANNOT_CONNECT,
+            ResultCode::RequestRejectedDifferentUserId => consts::SOCKS4_RESULT_REQUEST_REJECTED_DFFERENT_USER_ID,
+            ResultCode::Other(c) => c,
+        }
+    }
+
+    #[inline]
+    fn from_u8(code: u8) -> ResultCode {
+        match code {
+            consts::SOCKS4_RESULT_REQUEST_GRANTED => ResultCode::RequestGranted,
+            consts::SOCKS4_RESULT_REQUEST_REJECTED_OR_FAILED => ResultCode::RequestRejectedOrFailed,
+            consts::SOCKS4_RESULT_REQUEST_REJECTED_CANNOT_CONNECT => ResultCode::RequestRejectedCannotConnect,
+            consts::SOCKS4_RESULT_REQUEST_REJECTED_DFFERENT_USER_ID => ResultCode::RequestRejectedDifferentUserId,
+            code => ResultCode::Other(code),
+        }
+    }
+}
+
+impl fmt::Display for ResultCode {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            ResultCode::RequestGranted => f.write_str("request granted"),
+            ResultCode::RequestRejectedOrFailed => f.write_str("request rejected or failed"),
+            ResultCode::RequestRejectedCannotConnect => {
+                f.write_str("request rejected becasue SOCKS server cannot connect to identd on the client")
+            }
+            ResultCode::RequestRejectedDifferentUserId => {
+                f.write_str("request rejected because the client program and identd report different user-ids")
+            }
+            ResultCode::Other(code) => write!(f, "other result code {}", code),
+        }
+    }
+}
+
+/// SOCKS4 Address type
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub enum Address {
+    /// Socket address (IP Address)
+    SocketAddress(SocketAddrV4),
+    /// Domain name address
+    DomainNameAddress(String, u16),
+}
+
+impl fmt::Debug for Address {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Address::SocketAddress(ref addr) => write!(f, "{}", addr),
+            Address::DomainNameAddress(ref addr, ref port) => write!(f, "{}:{}", addr, port),
+        }
+    }
+}
+
+impl fmt::Display for Address {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Address::SocketAddress(ref addr) => write!(f, "{}", addr),
+            Address::DomainNameAddress(ref addr, ref port) => write!(f, "{}:{}", addr, port),
+        }
+    }
+}
+
+impl From<SocketAddrV4> for Address {
+    fn from(s: SocketAddrV4) -> Address {
+        Address::SocketAddress(s)
+    }
+}
+
+impl From<(String, u16)> for Address {
+    fn from((dn, port): (String, u16)) -> Address {
+        Address::DomainNameAddress(dn, port)
+    }
+}
+
+impl From<&Address> for Address {
+    fn from(addr: &Address) -> Address {
+        addr.clone()
+    }
+}
+
+impl From<Address> for socks5::Address {
+    fn from(addr: Address) -> socks5::Address {
+        match addr {
+            Address::SocketAddress(a) => socks5::Address::SocketAddress(SocketAddr::V4(a)),
+            Address::DomainNameAddress(d, p) => socks5::Address::DomainNameAddress(d, p),
+        }
+    }
+}
+
+/// Handshake Request
+///
+/// ```plain
+/// The client connects to the SOCKS server and sends a CONNECT/BIND request when
+/// it wants to establish a connection to an application server. The client
+/// includes in the request packet the IP address and the port number of the
+/// destination host, and userid, in the following format.
+///
+///                 +----+----+----+----+----+----+----+----+----+----+....+----+
+///                 | VN | CD | DSTPORT |      DSTIP        | USERID       |NULL|
+///                 +----+----+----+----+----+----+----+----+----+----+....+----+
+///  # of bytes:	   1    1      2              4           variable       1
+///
+/// VN is the SOCKS protocol version number and should be 4. CD is the
+/// SOCKS command code and should be 1 for CONNECT request, 2 for BIND request. NULL is a byte
+/// of all zero bits.
+/// ```
+#[derive(Debug, Clone)]
+pub struct HandshakeRequest {
+    pub cd: Command,
+    pub dst: Address,
+    pub user_id: Vec<u8>,
+}
+
+impl HandshakeRequest {
+    /// Read from a reader
+    pub async fn read_from<R>(r: &mut R) -> io::Result<HandshakeRequest>
+    where
+        R: AsyncBufRead + Unpin,
+    {
+        let mut buf = [0u8; 8];
+        let _ = r.read_exact(&mut buf).await?;
+
+        let vn = buf[0];
+        if vn != consts::SOCKS4_VERSION {
+            let err = Error::new(ErrorKind::InvalidData, format!("unsupported socks version {:#x}", vn));
+            return Err(err);
+        }
+
+        let cd = buf[1];
+        let command = match Command::from_u8(cd) {
+            Some(c) => c,
+            None => {
+                let err = Error::new(ErrorKind::InvalidData, format!("unsupported command {:#x}", cd));
+                return Err(err);
+            }
+        };
+
+        let port = BigEndian::read_u16(&buf[2..4]);
+
+        let mut user_id = Vec::new();
+        let _ = r.read_until(b'\0', &mut user_id).await?;
+        if user_id.is_empty() || user_id.last() != Some(&b'\0') {
+            return Err(ErrorKind::UnexpectedEof.into());
+        }
+        user_id.pop(); // Pops the last b'\0'
+
+        let dst = if buf[4] == 0x00 && buf[5] == 0x00 && buf[6] == 0x00 && buf[7] != 0x00 {
+            // SOCKS4a, indicates that it is a HOST address
+            let mut host = Vec::new();
+            let _ = r.read_until(b'\0', &mut host).await?;
+            if host.is_empty() || host.last() != Some(&b'\0') {
+                return Err(ErrorKind::UnexpectedEof.into());
+            }
+            host.pop(); // Pops the last b'\0'
+
+            match String::from_utf8(host) {
+                Ok(host) => Address::DomainNameAddress(host, port),
+                Err(..) => {
+                    let err = Error::new(ErrorKind::InvalidData, "invalid host encoding");
+                    return Err(err);
+                }
+            }
+        } else {
+            let ip = Ipv4Addr::new(buf[4], buf[5], buf[6], buf[7]);
+            Address::SocketAddress(SocketAddrV4::new(ip, port))
+        };
+
+        Ok(HandshakeRequest {
+            cd: command,
+            dst,
+            user_id,
+        })
+    }
+
+    /// Writes to buffer
+    pub fn write_to_buf<B: BufMut>(&self, buf: &mut B) {
+        debug_assert!(
+            !self.user_id.contains(&b'\0'),
+            "USERID shouldn't contain any NULL characters"
+        );
+
+        buf.put_u8(consts::SOCKS4_VERSION);
+        buf.put_u8(self.cd.as_u8());
+        match self.dst {
+            Address::SocketAddress(ref saddr) => {
+                let port = saddr.port();
+                buf.put_u16(port);
+                buf.put_slice(&saddr.ip().octets());
+
+                buf.put_slice(&self.user_id);
+                buf.put_u8(b'\0');
+            }
+            Address::DomainNameAddress(ref dname, port) => {
+                buf.put_u16(port);
+
+                // 0.0.0.x (x != 0)
+                const PLACEHOLDER: [u8; 4] = [0x00, 0x00, 0x00, 0xff];
+                buf.put_slice(&PLACEHOLDER);
+
+                buf.put_slice(&self.user_id);
+                buf.put_u8(b'\0');
+
+                buf.put_slice(dname.as_bytes());
+                buf.put_u8(b'\0');
+            }
+        }
+    }
+
+    /// Length in bytes
+    #[inline]
+    pub fn serialized_len(&self) -> usize {
+        let mut s = 1 + 1 + 2 + 4 + self.user_id.len() + 1; // USERID.LEN + NULL
+        if let Address::DomainNameAddress(ref dname, _) = self.dst {
+            s += dname.len() + 1;
+        }
+        s
+    }
+}
+
+/// Handshake Response
+///
+/// ```plain
+///             +----+----+----+----+----+----+----+----+
+///             | VN | CD | DSTPORT |      DSTIP        |
+///             +----+----+----+----+----+----+----+----+
+/// # of bytes:	   1    1      2              4
+/// ```
+#[derive(Debug, Clone)]
+pub struct HandshakeResponse {
+    pub cd: ResultCode,
+}
+
+impl HandshakeResponse {
+    /// Create a response with code
+    pub fn new(code: ResultCode) -> HandshakeResponse {
+        HandshakeResponse { cd: code }
+    }
+
+    /// Read from a reader
+    pub async fn read_from<R>(r: &mut R) -> io::Result<HandshakeResponse>
+    where
+        R: AsyncRead + Unpin,
+    {
+        let mut buf = [0u8; 8];
+        let _ = r.read_exact(&mut buf).await?;
+
+        let vn = buf[0];
+        if vn != consts::SOCKS4_VERSION {
+            let err = Error::new(ErrorKind::InvalidData, format!("unsupported socks version {:#x}", vn));
+            return Err(err);
+        }
+
+        let cd = buf[1];
+        let result_code = ResultCode::from_u8(cd);
+
+        // DSTPORT, DSTIP are ignored
+
+        Ok(HandshakeResponse { cd: result_code })
+    }
+
+    /// Write data into a writer
+    pub async fn write_to<W>(&self, w: &mut W) -> io::Result<()>
+    where
+        W: AsyncWrite + Unpin,
+    {
+        let mut buf = BytesMut::with_capacity(self.serialized_len());
+        self.write_to_buf(&mut buf);
+        w.write_all(&buf).await
+    }
+
+    /// Writes to buffer
+    pub fn write_to_buf<B: BufMut>(&self, buf: &mut B) {
+        let HandshakeResponse { ref cd } = *self;
+
+        buf.put_slice(&[
+            // VN: Result Code's version, must be 0
+            0x00,
+            // CD: Result Code
+            cd.as_u8(),
+            // DSTPORT: Ignored
+            0x00,
+            0x00,
+            // DSTIP: Ignored
+            0x00,
+            0x00,
+            0x00,
+            0x00,
+        ]);
+    }
+
+    /// Length in bytes
+    #[inline]
+    pub fn serialized_len(&self) -> usize {
+        1 + 1 + 2 + 4
+    }
+}
diff --git a/src/relay/tcprelay/local.rs b/src/relay/tcprelay/local.rs
index ebef5f02..6a1a7907 100644
--- a/src/relay/tcprelay/local.rs
+++ b/src/relay/tcprelay/local.rs
@@ -7,9 +7,11 @@ use crate::{config::ConfigType, context::SharedContext};
 /// Starts a TCP local server
 pub async fn run(context: SharedContext) -> io::Result<()> {
     match context.config().config_type {
+        ConfigType::Socks5Local => super::socks5_local::run(context).await,
+        #[cfg(feature = "local-socks4")]
+        ConfigType::Socks4Local => super::socks4_local::run(context).await,
         #[cfg(feature = "local-tunnel")]
         ConfigType::TunnelLocal => super::tunnel_local::run(context).await,
-        ConfigType::Socks5Local => super::socks5_local::run(context).await,
         #[cfg(feature = "local-http")]
         ConfigType::HttpLocal => super::http_local::run(context).await,
         #[cfg(feature = "local-redir")]
diff --git a/src/relay/tcprelay/mod.rs b/src/relay/tcprelay/mod.rs
index 06f3f2b9..253ebcfd 100644
--- a/src/relay/tcprelay/mod.rs
+++ b/src/relay/tcprelay/mod.rs
@@ -27,6 +27,7 @@ mod redir;
 #[cfg(feature = "local-redir")]
 mod redir_local;
 pub mod server;
+mod socks4_local;
 mod socks5_local;
 mod stream;
 #[cfg(feature = "local-tunnel")]
diff --git a/src/relay/tcprelay/proxy_stream.rs b/src/relay/tcprelay/proxy_stream.rs
index f6d80617..0b22cae1 100644
--- a/src/relay/tcprelay/proxy_stream.rs
+++ b/src/relay/tcprelay/proxy_stream.rs
@@ -463,6 +463,8 @@ async fn connect_proxy_server(context: &Context, svr_cfg: &ServerConfig) -> io::
         ConfigType::Server => svr_cfg.addr(),
 
         ConfigType::Socks5Local => svr_cfg.external_addr(),
+        #[cfg(feature = "local-socks4")]
+        ConfigType::Socks4Local => svr_cfg.external_addr(),
         #[cfg(feature = "local-tunnel")]
         ConfigType::TunnelLocal => svr_cfg.external_addr(),
         #[cfg(feature = "local-dns-relay")]
diff --git a/src/relay/tcprelay/socks4_local.rs b/src/relay/tcprelay/socks4_local.rs
new file mode 100644
index 00000000..f7562f32
--- /dev/null
+++ b/src/relay/tcprelay/socks4_local.rs
@@ -0,0 +1,181 @@
+//! Local server that accepts SOCKS4 protocol
+
+use std::{
+    io::{self, ErrorKind},
+    net::SocketAddr,
+};
+
+use futures::future::{self, Either};
+use log::{debug, error, info, trace, warn};
+use tokio::{
+    io::{AsyncWriteExt, BufReader},
+    net::{TcpListener, TcpStream},
+};
+
+use crate::{
+    context::SharedContext,
+    relay::{
+        loadbalancing::server::{PlainPingBalancer, ServerType, SharedPlainServerStatistic},
+        socks4::{Address, Command, HandshakeRequest, HandshakeResponse, ResultCode},
+        tcprelay::ProxyStream,
+    },
+};
+
+async fn handle_socks4_connect(
+    server: &SharedPlainServerStatistic,
+    mut stream: BufReader<TcpStream>,
+    client_addr: SocketAddr,
+    addr: &Address,
+) -> io::Result<()> {
+    let context = server.context();
+    let svr_cfg = server.server_config();
+
+    // NOTE: Shadowsocks server uses SOCKS5 Address
+    let ss_addr = From::from(addr.clone());
+
+    let mut svr_s = match ProxyStream::connect(server.clone_context(), svr_cfg, &ss_addr).await {
+        Ok(svr_s) => {
+            // Tell the client that we are ready
+            let handshake_rsp = HandshakeResponse::new(ResultCode::RequestGranted);
+            handshake_rsp.write_to(&mut stream).await?;
+
+            trace!("sent header: {:?}", handshake_rsp);
+
+            svr_s
+        }
+        Err(perr) => {
+            if perr.is_proxied() {
+                // Report to global statistic
+                server.report_failure().await;
+            }
+
+            let err = perr.into_inner();
+            let result_code = match err.kind() {
+                ErrorKind::ConnectionRefused => ResultCode::RequestRejectedCannotConnect,
+                ErrorKind::ConnectionAborted => ResultCode::RequestRejectedCannotConnect,
+                _ => ResultCode::RequestRejectedOrFailed,
+            };
+
+            let handshake_rsp = HandshakeResponse::new(result_code);
+            handshake_rsp.write_to(&mut stream).await?;
+
+            return Err(err);
+        }
+    };
+
+    // NOTE: Transfer all buffered data before unwrap, or these data will be lost
+    let buffer = stream.buffer();
+    if !buffer.is_empty() {
+        svr_s.write_all(buffer).await?;
+    }
+
+    // UNWRAP.
+    let mut stream = stream.into_inner();
+
+    // Reset `TCP_NODELAY` after Socks5 handshake
+    if !context.config().no_delay {
+        if let Err(err) = stream.set_nodelay(false) {
+            error!("failed to reset TCP_NODELAY on socket, error: {:?}", err);
+        }
+    }
+
+    let (mut svr_r, mut svr_w) = svr_s.split();
+    let (mut r, mut w) = stream.split();
+
+    use tokio::io::copy;
+
+    let rhalf = copy(&mut r, &mut svr_w);
+    let whalf = copy(&mut svr_r, &mut w);
+
+    debug!("CONNECT relay established {} <-> {}", client_addr, addr);
+
+    match future::select(rhalf, whalf).await {
+        Either::Left((Ok(..), _)) => trace!("CONNECT relay {} -> {} closed", client_addr, addr),
+        Either::Left((Err(err), _)) => {
+            if let ErrorKind::TimedOut = err.kind() {
+                trace!("CONNECT relay {} -> {} closed with error {}", client_addr, addr, err);
+            } else {
+                error!("CONNECT relay {} -> {} closed with error {}", client_addr, addr, err);
+            }
+        }
+        Either::Right((Ok(..), _)) => trace!("CONNECT relay {} <- {} closed", client_addr, addr),
+        Either::Right((Err(err), _)) => {
+            if let ErrorKind::TimedOut = err.kind() {
+                trace!("CONNECT relay {} <- {} closed with error {}", client_addr, addr, err);
+            } else {
+                error!("CONNECT relay {} <- {} closed with error {}", client_addr, addr, err);
+            }
+        }
+    }
+
+    debug!("CONNECT relay {} <-> {} closed", client_addr, addr);
+
+    Ok(())
+}
+
+async fn handle_socks4_client(server: &SharedPlainServerStatistic, s: TcpStream) -> io::Result<()> {
+    let svr_cfg = server.server_config();
+
+    if let Err(err) = s.set_keepalive(svr_cfg.timeout()) {
+        error!("failed to set keep alive: {:?}", err);
+    }
+
+    // Enable TCP_NODELAY for quick handshaking
+    if let Err(err) = s.set_nodelay(true) {
+        error!("failed to set TCP_NODELAY on accepted socket, error: {:?}", err);
+    }
+
+    let client_addr = s.peer_addr()?;
+
+    // NOTE: Wraps it with BufReader for reading NULL terminated informations in HandshakeRequest
+    let mut s = BufReader::new(s);
+    let handshake_req = HandshakeRequest::read_from(&mut s).await?;
+
+    trace!("socks4 {:?}", handshake_req);
+
+    match handshake_req.cd {
+        Command::Connect => {
+            debug!("CONNECT {}", handshake_req.dst);
+
+            handle_socks4_connect(server, s, client_addr, &handshake_req.dst).await
+        }
+        Command::Bind => {
+            warn!("BIND is not supported");
+
+            let handshake_rsp = HandshakeResponse::new(ResultCode::RequestRejectedOrFailed);
+            handshake_rsp.write_to(&mut s).await?;
+
+            Ok(())
+        }
+    }
+}
+
+/// Starts a TCP local server with Socks4 proxy protocol
+pub async fn run(context: SharedContext) -> io::Result<()> {
+    let local_addr = context.config().local_addr.as_ref().expect("local config");
+    let bind_addr = local_addr.bind_addr(&context).await?;
+
+    let mut listener = TcpListener::bind(&bind_addr)
+        .await
+        .unwrap_or_else(|err| panic!("failed to listen on {}, {}", local_addr, err));
+
+    let actual_local_addr = listener.local_addr().expect("determine port bound to");
+
+    let servers = PlainPingBalancer::new(context, ServerType::Tcp).await;
+
+    info!("shadowsocks TCP listening on {}", actual_local_addr);
+
+    loop {
+        let (socket, peer_addr) = listener.accept().await?;
+        let server = servers.pick_server();
+
+        trace!("got connection {}", peer_addr);
+        trace!("picked proxy server: {:?}", server.server_config());
+
+        tokio::spawn(async move {
+            if let Err(err) = handle_socks4_client(&server, socket).await {
+                error!("TCP socks4 client exited with error: {}", err);
+            }
+        });
+    }
+}
diff --git a/src/relay/tcprelay/socks5_local.rs b/src/relay/tcprelay/socks5_local.rs
index 17fab786..a68728a3 100644
--- a/src/relay/tcprelay/socks5_local.rs
+++ b/src/relay/tcprelay/socks5_local.rs
@@ -1,4 +1,4 @@
-//! Local server that accepts SOCKS 5 protocol
+//! Local server that accepts SOCKS5 protocol
 
 use std::{
     io::{self, ErrorKind},
@@ -28,7 +28,7 @@ struct UdpConfig {
     client_addr: SocketAddr,
 }
 
-async fn handle_socks5_connect<'a>(
+async fn handle_socks5_connect(
     server: &SharedPlainServerStatistic,
     stream: &mut TcpStream,
     client_addr: SocketAddr,
@@ -86,7 +86,7 @@ async fn handle_socks5_connect<'a>(
     let rhalf = copy(&mut r, &mut svr_w);
     let whalf = copy(&mut svr_r, &mut w);
 
-    debug!("CONNECT relay established {} <-> {}", client_addr, addr,);
+    debug!("CONNECT relay established {} <-> {}", client_addr, addr);
 
     match future::select(rhalf, whalf).await {
         Either::Left((Ok(..), _)) => trace!("CONNECT relay {} -> {} closed", client_addr, addr),
diff --git a/src/relay/udprelay/local.rs b/src/relay/udprelay/local.rs
index a6ae07b8..147b906b 100644
--- a/src/relay/udprelay/local.rs
+++ b/src/relay/udprelay/local.rs
@@ -20,9 +20,11 @@ pub async fn run(context: SharedContext) -> io::Result<()> {
     }
 
     match context.config().config_type {
+        ConfigType::Socks5Local => super::socks5_local::run(context).await,
+        #[cfg(feature = "local-socks4")]
+        ConfigType::Socks4Local => unreachable!(),
         #[cfg(feature = "local-tunnel")]
         ConfigType::TunnelLocal => super::tunnel_local::run(context).await,
-        ConfigType::Socks5Local => super::socks5_local::run(context).await,
         #[cfg(feature = "local-redir")]
         ConfigType::RedirLocal => super::redir_local::run(context).await,
         #[cfg(feature = "local-http")]