Go socket

在GO的net包中定义了很多对网络编程操作的方法.

比如操作IP,输入IP格式地址,返回IP

package main
import (
	"net"
	"os"
	"fmt"
)
func main() {
	if len(os.Args) != 2 {
		fmt.Fprintf(os.Stderr, "Usage: %s ip-addr\n", os.Args[0])
		os.Exit(1)
	}
	name := os.Args[1]
	addr := net.ParseIP(name)
	if addr == nil {
		fmt.Println("Invalid address")
	} else {
		fmt.Println("The address is ", addr.String())
	}
	os.Exit(0)
}

客户端代码

package main

import (
	"fmt"
	"io/ioutil"
	"net"
	"os"
)

func main() {
	if len(os.Args) != 2 {
		fmt.Fprintf(os.Stderr, "Usage: %s host:port ", os.Args[0])
		os.Exit(1)
	}
	service := os.Args[1]
	tcpAddr, err := net.ResolveTCPAddr("tcp4", service)  //获取一个IP地址转成格式
	checkError(err)
	conn, err := net.DialTCP("tcp", nil, tcpAddr)   //连接服务器,协议,本机地址,目的地址,本机地址一般为nil
	checkError(err)
	_, err = conn.Write([]byte("HEAD / HTTP/1.0\r\n\r\n"))   //请求头写进去,协议格式要把换行写清楚
	checkError(err)
	result, err := ioutil.ReadAll(conn)
	checkError(err)
	fmt.Println(string(result))
	os.Exit(0)
}
func checkError(err error) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "Fatal error: %s", err.Error())
		os.Exit(1)
	}
}

然后是tcp服务端

package main

import (
	"fmt"
	"net"
	"os"
	"time"
)

func main() {
	service := ":7777"
	tcpAddr, err := net.ResolveTCPAddr("tcp4", service)   //转换IP地址格式
	checkError(err)
	listener, err := net.ListenTCP("tcp", tcpAddr)  //监听端口
	checkError(err)
	for {
		conn, err := listener.Accept()   //等等连接
		if err != nil {
			continue
		}
		daytime := time.Now().String()
		conn.Write([]byte(daytime)) // don't care about return value
		conn.Close()                // we're finished with this client
	}
}
func checkError(err error) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "Fatal error: %s", err.Error())
		os.Exit(1)
	}
}

然后是加了goroutine的服务端

package main

import (
	"fmt"
	"net"
	"os"
	"time"
)

func main() {
	service := ":1200"
	tcpAddr, err := net.ResolveTCPAddr("tcp4", service)
	checkError(err)
	listener, err := net.ListenTCP("tcp", tcpAddr)
	checkError(err)
	for {
		conn, err := listener.Accept()
		if err != nil {
			continue
		}
		go handleClient(conn)   //每次有用户连接就启动一个单独的goroutine来处理,可以处理多用户,彼此保持独立性.
	}
}

func handleClient(conn net.Conn) {
	defer conn.Close()            //结束完后关闭连接,就是关闭用户的套接字.
	daytime := time.Now().String()
	conn.Write([]byte(daytime)) // don't care about return value
	// we're finished with this client
}
func checkError(err error) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "Fatal error: %s", err.Error())
		os.Exit(1)
	}
}

加个长连接,判断超时

package main

import (
	"fmt"
	"net"
	"os"
	"time"
	"strconv"
	"strings"
)

func main() {
	service := ":1200"
	tcpAddr, err := net.ResolveTCPAddr("tcp4", service)
	checkError(err)
	listener, err := net.ListenTCP("tcp", tcpAddr)
	checkError(err)
	for {
		conn, err := listener.Accept()
		if err != nil {
			continue
		}
		go handleClient(conn)
	}
}

func handleClient(conn net.Conn) {
	conn.SetReadDeadline(time.Now().Add(2 * time.Minute)) // set 2 minutes timeout
	request := make([]byte, 128) // set maxium request length to 128B to prevent flood attack
	defer conn.Close()  // close connection before exit
	for {
		read_len, err := conn.Read(request)  //读取连接用户发送过来的内容,括号中为大小

		if err != nil {
			fmt.Println(err)
			break
		}

    		if read_len == 0 {
    			break // connection already closed by client
    		} else if strings.TrimSpace(string(request[:read_len])) == "timestamp" {
    			daytime := strconv.FormatInt(time.Now().Unix(), 10)
    			conn.Write([]byte(daytime))
    		} else {
    			daytime := time.Now().String()
    			conn.Write([]byte(daytime))
    		}

    		request = make([]byte, 128) //清除内容,开始下一次
	}
}

func checkError(err error) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "Fatal error: %s", err.Error())
		os.Exit(1)
	}
}

再就是UDP客户端

package main

import (
	"fmt"
	"net"
	"os"
)

func main() {
	if len(os.Args) != 2 {
		fmt.Fprintf(os.Stderr, "Usage: %s host:port", os.Args[0])
		os.Exit(1)
	}
	service := os.Args[1]
	udpAddr, err := net.ResolveUDPAddr("udp4", service)  //转换IP地址
	checkError(err)
	conn, err := net.DialUDP("udp", nil, udpAddr)   //UDP连接
	checkError(err)
	_, err = conn.Write([]byte("anything"))  //发送内容
	checkError(err)
	var buf [512]byte
	n, err := conn.Read(buf[0:])   //读取响应内容
	checkError(err)
	fmt.Println(string(buf[0:n]))
	os.Exit(0)
}
func checkError(err error) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "Fatal error ", err.Error())
		os.Exit(1)
	}
}

udp服务器

package main

import (
	"fmt"
	"net"
	"os"
	"time"
)

func main() {
	service := ":1200"
	udpAddr, err := net.ResolveUDPAddr("udp4", service)   //转换IP地址格式
	checkError(err)
	conn, err := net.ListenUDP("udp", udpAddr)   //监听IP和地址
	checkError(err)
	for {
		handleClient(conn)
	}
}
func handleClient(conn *net.UDPConn) {
	var buf [512]byte
	_, addr, err := conn.ReadFromUDP(buf[0:])   //读取接收的内容
	if err != nil {
		return
	}
	daytime := time.Now().String()
	conn.WriteToUDP([]byte(daytime), addr)   //回复内容
}
func checkError(err error) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "Fatal error ", err.Error())
		os.Exit(1)
	}
}