Simple TCP programming in the Go language

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

Pre-preparation

• Need a import "net" Package
• IPType, one of the important methods is IP.ParseIP(ipaddr string) to determine whether it is a legitimate IP address

TCP Client

• func (c *TCPConn) Write(b []byte) (n int, err os.Error)Used to send data, return the length of data sent or return an error, is TCPConn the method
• func (c *TCPConn) Read(b []byte) (n int, err os.Error)The method used to receive data, return the length of the receive, or return an error. TCPConn

• TCPAddrType, save address information for TCP, including address and port

    type TCPAddr struct {      IP IP      Port int  }

• func ResolveTCPAddr(net, addr string) (*TCPAddr, os.Error)Get one TCPAddr , the parameters are all string types, net is a, const string including, tcp4 tcp6 tcp generally used tcp , compatible with V4 and V6, addr representing IP addresses, including port numbers, such as www.google.com:80
• func DialTCP(net string, laddr, raddr *TCPAddr) (c *TCPConn, err os.Error)Used to connect (connect) to a remote server, net means the protocol tcp , tcp4 or tcp6 , a laddr native address, typically nil , represents a raddr remote address, here laddr and raddr all TCPAddrtype, which is typically the return value of the previous function.

• As a TCP client, the basic operation flow is as follows:

    service="www.google.com:80"  tcpAddr, err := net.ResolveTCPAddr("tcp4", service)  conn, err := net.DialTCP("tcp", nil, tcpAddr)  _, err = conn.Write([]byte("HEAD / HTTP/1.0\r\n\r\n"))  _, err = conn.Read(b) / result, err := ioutil.ReadAll(conn)

TCP Server

• func ListenTCP(net string, laddr *TCPAddr) (l *TCPListener, err os.Error)Used to listen to a port, to net indicate a protocol type, to laddr represent a native address, to be a TCPAddr type, note that the laddr here include a port, return a *TCPListener type or error
• func (l *TCPListener) Accept() (c Conn, err os.Error)Used to return a new connection for subsequent operations, this is TCPListener the method that is generally TCPListener returned from the previous function.

• The basic operating procedures for the server are:

    service:=":9090"  tcpAddr, err := net.ResolveTCPAddr("tcp4", service)  l,err := net.ListenTCP("tcp",tcpAddr)  conn,err := l.Accept()  go Handler(conn) //此处使用go关键字新建线程处理连接，实现并发

An example

Demand

Implement a public chat server.

• server receives client-side information
• Sends the client's information to all clients after it has been received
• Client uses /quit exit Chat
• Use only one set of code to start a server or client with command-line arguments

implementation:

Package Mainimport ("FMT" "OS" "NET")////////////////////////////////////////////////////////////error checking///////////// Func checkerror (Err Error,info string) (res bool) {if (err! = nil) {FMT. Println (info+ "" + Err. Error ()) return False}return true}////////////////////////////////////////////////////////////server-side receive data thread//parameter:// Data connection conn//communication channel Messages//////////////////////////////////////////////////////////func Handler (Conn net. Conn,messages Chan string) {fmt. PRINTLN ("Connection is connected from ...", Conn. Remoteaddr (). String ()) BUF: = make ([]byte,1024) for{lenght, err: = conn. Read (BUF) if (CheckError (Err, "Connection") ==false) {Conn. Close () break}if lenght > 0{buf[lenght]=0}//fmt. Println ("rec[", Conn. Remoteaddr (). String (), "] Say:", String (buf[0:lenght)) Recivestr: =string (Buf[0:lenght]) messages <-recivestr}}/////////////// The server sends the data thread////parameter//connection dictionary conns//data channel messages//////////////////////// //////////////////////Func Echohandler (Conns *map[string]net. Conn,messages Chan string) {for{msg:= <-messagesfmt. PRINTLN (msg) for Key,value: = Range *conns {fmt. PRINTLN ("Connection is connected from ...", key) _,err: =value. Write ([]byte (msg)) if (err! = nil) {FMT. Println (Err. Error ()) Delete (*conns,key)}}}}////////////////////////////////////////////////////////////start server//Parameter//Port port/// Func startserver (Port string) {service:= ":" +port//strconv. Itoa (port); Tcpaddr, err: = Net. RESOLVETCPADDR ("TCP4", Service) CheckError (err, "resolvetcpaddr") L,err: = Net. LISTENTCP ("TCP", TCPADDR) checkerror (err, "listentcp") Conns:=make (map[string]net. CONN) Messages: = Make (chan string,10)//Start server broadcast thread go Echohandler (&conns,messages) for {fmt. Println ("Listening ...") Conn,err: = L.accept () checkerror (err, "Accept") fmt. Println ("Accepting ...") conns[conn. Remoteaddr (). String ()]=conn//start a new thread go Handler (conn,messages)}}//////////////////////////////////////////////////////////// CustomerEnd send thread//parameter//Send connection Conn//////////////////////////////////////////////////////////func chatsend (conn net. Conn) {var input stringusername: = Conn. Localaddr (). String () for {fmt. SCANLN (&input) if input = = "/quit" {fmt. Println ("Byebye..") Conn. Close () OS. Exit (0);} Lens,err: =conn. Write ([]byte (username + "Say:::" + input)] FMT. PRINTLN (Lens) if (err! = nil) {FMT. Println (Err. Error ()) Conn. Close () break}}}////////////////////////////////////////////////////////////client startup function//parameter//remote IP address and port tcpaddr////// Func startclient (tcpaddr string) {tcpaddr, err: = Net. RESOLVETCPADDR ("TCP4", tcpaddr) checkerror (err, "RESOLVETCPADDR") conn, err: = Net. DIALTCP ("TCP", Nil, tcpaddr) checkerror (err, "dialtcp")//Start client send thread go chatsend (conn)//Start client rotation buf: = make ([]byte,1024) For{lenght, ERR: = conn. Read (BUF) if (CheckError (Err, "Connection") ==false) {Conn. Close () fmt. Println ("Server is dead ... Byebye ") os. Exit (0)}fmt. Println (String (buf[0:lenght))}}////////////////////////////////////////////Main program////parameter description://Start server side: Chat Server [port]eg:chat server 9090//start client: chat client [Server Ip Addr]:[ser Ver Port] Eg:chat client 192.168.0.74:9090//////////////////////////////////////////////////////////func main () {if Len (OS. Args)!=3 {fmt. Println ("Wrong pare") os. Exit (0)}if OS. args[1]== "Server" && len (OS. Args) ==3 {startserver (OS. ARGS[2])}if OS. args[1]== "Client" && len (OS. Args) ==3 {startclient (OS. ARGS[2])}}