(Forty-six) golang-- Network Programming (simple chat system)

Go is one of the main objectives for large-scale back-end service program, this is a network communications server program is essential to a key part.

Network programming in two ways:

(1) TCP Socket Programming: mainstream network programming, was called TCP Socket programming, because the bottom is based on TCP / IP protocols;

(2) Programming http B / S structure, when using the browser to access the server, the http protocol is used, the http tcp socket bottom is achieved;

Communication between computers need, must have a network cable, network card or wireless network card;

TCP / IP model: an application layer, transport layer, network layer, data link layer, physical layer;

IP address: hosts and routers on the internet has an ip address each, which comprises a network number and host number, ip address has ipv4 (32 bit) or ipv6 (128 bits) can be viewed Ipconfig.

Port: The port, especially tcp / ip protocol on the logical sense of the port. Total 256 × 256-1 = 65535 ports;

Port Category:

0 is reserved port;
1-1024 is a fixed-port (22: ssh remote login protocol, 23: telnet use, 21: ftp use, 25: smtp service use, 80: lis use, 7: echo service)
1025-65535: a dynamic port, for programmers to use;

A block diagram of the communication between the server and the client:

As can be seen, the communication between them is by port (because it is simple communications, the current client does not communicate directly, only through the client)

server.go

package main

import (
    "fmt"
    "net"
)

func process(conn net.Conn) {
    //这里接受客户端的数据
    defer conn.Close()
    for {
        //创建一个新的切片
        buf := make([]byte, 1024)
        //等待客户端发送信息，如果客户端没发送，协程就阻塞在这
        // fmt.Printf("服务器在等待客户端%v的输入\n", conn.RemoteAddr().String())
        n, err := conn.Read(buf)
        if err != nil {
            // fmt.Println("服务器read err=", err)
            fmt.Println("客户端退出了")
            return
        }
        //显示客户端发送内容到服务器的终端
        fmt.Print(string(buf[:n]) + "\n")

    }
}

func main() {
    fmt.Println("服务器开始监听...")
    //协议、端口
    listen, err := net.Listen("tcp", "0.0.0.0:8888")
    if err != nil {
        fmt.Println("监听失败,err=", err)
        return
    }
    //延时关闭
    defer listen.Close()
    for {
        //循环等待客户端连接
        fmt.Println("等待客户端连接...")
        conn, err := listen.Accept()
        if err != nil {
            fmt.Println("Accept() err=", err)
        } else {
            fmt.Printf("Accept() suc con=%v,客户端Ip=%v\n", conn, conn.RemoteAddr().String())
        }
        //这里准备起个协程为客户端服务
        go process(conn)
    }
    //fmt.Printf("监听成功，suv=%v\n", listen)
}

client.go

package main

import (
    "bufio"
    "fmt"
    "net"
    "os"
    "strings"
)

func main() {
    //同样是tcp协议，192.168.1.145服务端的ip地址，这里是我自己本机的地址，可在终端用ipconfig查看，后面是服务端开启的端口号
    conn, err := net.Dial("tcp", "192.168.1.145:8888")
    if err != nil {
        fmt.Println("client dial err=", err)
        return
    }
    //哭护短在命令行输入单行数据
    reader := bufio.NewReader(os.Stdin)
    for {
        //从终端读取一行用户的输入，并发给服务器
        line, err := reader.ReadString('\n')
        if err != nil {
            fmt.Println("readString err=", err)
        }
        //去掉输入后的换行符
        line = strings.Trim(line, "\r\n")
        //如果是exit,则退出客户端
        if line == "exit" {
            fmt.Println("客户端退出了")
            break
        }
        //将line发送给服务器
        _, e := conn.Write([]byte(line))
        if e != nil {
            fmt.Println("conn.write err=", e)
        }
        // fmt.Printf("客户端发送了%d字节的数据，并退出", n)
    }
}