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A fresh implementation of Shadowsocks in Go.

GoDoc at

Build and test


  • SOCKS5 proxy with UDP Associate
  • Support for Netfilter TCP redirect on Linux (IPv6 should work but not tested)
  • Support for Packet Filter TCP redirect on MacOS/Darwin (IPv4 only)
  • UDP tunneling (e.g. relay DNS packets)
  • TCP tunneling (e.g. benchmark with iperf3)
  • SIP003 plugins
  • Replay attack mitigation


Pre-built binaries for common platforms are available at

Install from source

go get -u -v

Basic Usage


Start a server listening on port 8488 using AEAD_CHACHA20_POLY1305 AEAD cipher with password your-password.

go-shadowsocks2 -s 'ss://AEAD_CHACHA20_POLY1305:your-password@:8488' -verbose


Start a client connecting to the above server. The client listens on port 1080 for incoming SOCKS5 connections, and tunnels both UDP and TCP on port 8053 and port 8054 to and respectively.

go-shadowsocks2 -c 'ss://AEAD_CHACHA20_POLY1305:your-password@[server_address]:8488' \
    -verbose -socks :1080 -u -udptun :8053=,:8054= \
                             -tcptun :8053=,:8054=

Replace [server_address] with the server's public address.

Advanced Usage

Netfilter TCP redirect on Linux

The client offers -redir and -redir6 (for IPv6) options to handle TCP connections redirected by Netfilter on Linux. The feature works similar to ss-redir from shadowsocks-libev.

Start a client listening on port 1082 for redirected TCP connections and port 1083 for redirected TCP IPv6 connections.

go-shadowsocks2 -c 'ss://AEAD_CHACHA20_POLY1305:your-password@[server_address]:8488' -redir :1082 -redir6 :1083

TCP tunneling

The client offers -tcptun [local_addr]:[local_port]=[remote_addr]:[remote_port] option to tunnel TCP. For example it can be used to proxy iperf3 for benchmarking.

Start iperf3 on the same machine with the server.

iperf3 -s

By default iperf3 listens on port 5201.

Start a client on the same machine with the server. The client listens on port 1090 for incoming connections and tunnels to localhost:5201 where iperf3 is listening.

go-shadowsocks2 -c 'ss://AEAD_CHACHA20_POLY1305:your-password@[server_address]:8488' -tcptun :1090=localhost:5201

Start iperf3 client to connect to the tunneld port instead

iperf3 -c localhost -p 1090

SIP003 Plugins (Experimental)

Both client and server support SIP003 plugins. Use -plugin and -plugin-opts parameters to enable.


go-shadowsocks2 -c 'ss://AEAD_CHACHA20_POLY1305:your-password@[server_address]:8488' \
    -verbose -socks :1080 -u -plugin v2ray


go-shadowsocks2 -s 'ss://AEAD_CHACHA20_POLY1305:your-password@:8488' -verbose \
    -plugin v2ray -plugin-opts "server"


It will look for the plugin in the current directory first, then $PATH.

UDP connections will not be affected by SIP003.

Replay Attack Mitigation

By default a Bloom filter is deployed to defend against replay attacks. Use the following environment variables to fine-tune the mechanism:

  • SHADOWSOCKS_SF_CAPACITY: Number of recent connections to track. Default 1e6 (one million). Setting it to 0 disables the feature.
  • SHADOWSOCKS_SF_FPR: False positive rate of the Bloom filter. Default 1e-6 (0.0001%). This should be enough for most cases.
  • SHADOWSOCKS_SF_SLOT: The Bloom filter is divided into a number (default 10) of slots. When the Bloom filter is full, the oldest slot will be cleared for recycling. In general you should not change this number unless you understand what you are doing.

Design Principles

The code base strives to

  • be idiomatic Go and well organized;
  • use fewer external dependences as reasonably possible;
  • only include proven modern ciphers;
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