KCP - A Fast and Reliable ARQ Protocol

KCP is a fast and reliable protocol that can achieve the transmission effect of a reduction of the average latency by 30% to 40% and reduction of the maximum delay by a factor of three, at the cost of 10% to 20% more bandwidth wasted than TCP. It is implemented by using the pure algorithm, and is not responsible for the sending and receiving of the underlying protocol (such as UDP), requiring the users to define their own transmission mode for the underlying data packet, and provide it to KCP in the way of callback. Even the clock needs to be passed in from the outside, without any internal system calls.

The entire protocol has only two source files of ikcp.h, ikcp.c, which can be easily integrated into the user’s own protocol stack. You may have implement a P2P, or a UDP-based protocol, but are lack of a set of perfect ARQ reliable protocol implementation, then by simply copying the two files to the existing project, and writing a couple of lines of code, you can use it.

GitHub: https://github.com/skywind3000/kcp

kcptun - A Secure Tunnel Based On KCP with N:M Multiplexing

QuickStart

Download precompiled Releases.

KCP Client: 

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./client_darwin_amd64 -r "KCP_SERVER_IP:4000" -l ":8388" -mode fast2

KCP Server:

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./server_linux_amd64 -t "TARGET_IP:8388" -l ":4000" -mode fast2

Application -> KCP Client(8388/tcp) -> KCP Server(4000/udp) -> Server(8388/tcp)

Usage:

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$ ./client_darwin_amd64 -h
NAME:
   kcptun - client(with SMUX)

USAGE:
   client_darwin_amd64 [global options] command [command options] [arguments...]

VERSION:
   20170120

COMMANDS:
     help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --localaddr value, -l value      local listen address (default: ":12948")
   --remoteaddr value, -r value     kcp server address (default: "vps:29900")
   --key value                      pre-shared secret between client and server (default: "it's a secrect") [$KCPTUN_KEY]
   --crypt value                    aes, aes-128, aes-192, salsa20, blowfish, twofish, cast5, 3des, tea, xtea, xor, none (default: "aes")
   --mode value                     profiles: fast3, fast2, fast, normal (default: "fast")
   --conn value                     set num of UDP connections to server (default: 1)
   --autoexpire value               set auto expiration time(in seconds) for a single UDP connection, 0 to disable (default: 0)
   --mtu value                      set maximum transmission unit for UDP packets (default: 1350)
   --sndwnd value                   set send window size(num of packets) (default: 128)
   --rcvwnd value                   set receive window size(num of packets) (default: 512)
   --datashard value, --ds value    set reed-solomon erasure coding - datashard (default: 10)
   --parityshard value, --ps value  set reed-solomon erasure coding - parityshard (default: 3)
   --dscp value                     set DSCP(6bit) (default: 0)
   --nocomp                         disable compression
   --snmplog value                  collect snmp to file, aware of timeformat in golang, like: ./snmp-20060102.log
   --snmpperiod value               snmp collect period, in seconds (default: 60)
   --log value                      specify a log file to output, default goes to stderr
   -c value                         config from json file, which will override the command from shell
   --help, -h                       show help
   --version, -v                    print the version

$ ./server_darwin_amd64 -h
NAME:
   kcptun - server(with SMUX)

USAGE:
   server_darwin_amd64 [global options] command [command options] [arguments...]

VERSION:
   20170120

COMMANDS:
     help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --listen value, -l value         kcp server listen address (default: ":29900")
   --target value, -t value         target server address (default: "127.0.0.1:12948")
   --key value                      pre-shared secret between client and server (default: "it's a secrect") [$KCPTUN_KEY]
   --crypt value                    aes, aes-128, aes-192, salsa20, blowfish, twofish, cast5, 3des, tea, xtea, xor, none (default: "aes")
   --mode value                     profiles: fast3, fast2, fast, normal (default: "fast")
   --mtu value                      set maximum transmission unit for UDP packets (default: 1350)
   --sndwnd value                   set send window size(num of packets) (default: 1024)
   --rcvwnd value                   set receive window size(num of packets) (default: 1024)
   --datashard value, --ds value    set reed-solomon erasure coding - datashard (default: 10)
   --parityshard value, --ps value  set reed-solomon erasure coding - parityshard (default: 3)
   --dscp value                     set DSCP(6bit) (default: 0)
   --nocomp                         disable compression
   --snmplog value                  collect snmp to file, aware of timeformat in golang, like: ./snmp-20060102.log
   --snmpperiod value               snmp collect period, in seconds (default: 60)
   --log value                      specify a log file to output, default goes to stderr
   -c value                         config from json file, which will override the command from shell
   --help, -h                       show help
   --version, -v                    print the version

Concept

ss-client <-> local kcptun client <-> server kcptun server <-> ss-server