Golang Implementing a TCP forwarding Agent

This is a creation in Article, where the information may have evolved or changed.

Package Mainimport ("Flag" "FMT" "IO" "NET" "OS" "Strings" "Sync") var lock sync. Mutexvar truelist []stringvar IP Stringvar list stringfunc main () {flag. Stringvar (&ip, "L", ": 9897", "-l=0.0.0.0:9897 specifies the port the service listens to") flag. Stringvar (&list, "D", "127.0.0.1:1789,127.0.0.1:1788", "-d=127.0.0.1:1789,127.0.0.1:1788 specifies the backend IP and port, multiple uses ', ' separated ') Flag. Parse () Truelist = strings. Split (List, ",") If Len (truelist) <= 0 {fmt. PRINTLN ("Backend IP and port cannot be empty, or invalid") OS. Exit (1)}server ()}func server () {lis, err: = Net. Listen ("tcp", IP) if err! = Nil {fmt. PRINTLN (Err) return}defer lis. Close () for {conn, err: = Lis. Accept () if err! = Nil {fmt. PRINTLN ("Establish connection error:%v\n", err) continue}fmt. PRINTLN (Conn. Remoteaddr (), Conn. LOCALADDR ()) go handle (conn)}}func handle (sconn net. Conn) {defer sconn. Close () IP, OK: = GetIP () If!ok {return}dconn, err: = Net. Dial ("tcp", IP) if err! = Nil {fmt. Printf ("Connection%v failed:%v\n", IP, err) Return}exitchan: = Make (chan bool, 1) go func (sconn net. Conn, Dconn net. Conn, Exit chan bool) {_, Err: = Io. Copy (Dconn, sconn) fmt. Printf ("Send data to%v failed:%v\n", IP, Err) Exitchan <-true} (sconn, Dconn, Exitchan) go func (sconn net. Conn, Dconn net. Conn, Exit chan bool) {_, Err: = Io. Copy (sconn, Dconn) fmt. Printf ("Failed to receive data from%v:%v\n", IP, Err) Exitchan <-true} (sconn, Dconn, Exitchan) <-exitchandconn.close ()}func GetIP () ( String, bool) {lock. Lock () defer lock. Unlock () If Len (truelist) < 1 {return "", false}ip: = Truelist[0]truelist = Append (truelist[1:], IP) return IP, True}