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Server：echoServer.go
/** * File: echoServer.go * Author: 蛇叔 * 公众号: 蛇叔编程心法(snakeCodeHeart) */ package main import (   "fmt"   "net"   "os"   "syscall" ) const (   PORT = 8888   ADDR = "127.0.0.1"   SIZE = 100 ) func main() {   // 1. create socketfd   socketFd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_STREAM, 0)   if err != nil || socketFd < 0 {     fmt.Println("socket create err: ", err)     os.Exit(-1)   }   // 2. bind addr and port   ip4 := net.ParseIP(ADDR).To4()   if ip4 == nil {     fmt.Println("net.ParseIP err")     os.Exit(-1)   }   sa := &syscall.SockaddrInet4{Port: PORT}   copy(sa.Addr[:], ip4)   err = syscall.Bind(socketFd, sa)   if err != nil {     fmt.Println("socket bind err: ", err)     os.Exit(-1)   }   // 3. listen   err = syscall.Listen(socketFd, 128)   if err != nil {     fmt.Println("socket listen err: ", err)     os.Exit(-1)   }   // 4. accept   acceptFd, _, err := syscall.Accept(socketFd)   if err != nil {     fmt.Println("socket accept err: ", err)     os.Exit(-1)   }   var (     buf = make([]byte, SIZE)     readn int     err2 error   )   for {     // 5. read data     readn, err2 = syscall.Read(acceptFd, buf)     if err2 != nil {       break     }     if readn > 0 {       // 6. write data       writen, _ := syscall.Write(acceptFd, buf[:readn])       if writen < 0 {         fmt.Println("socket write err: ", err)         break       }     } else if readn == 0 {       fmt.Println("客户端已关闭")       break     } else if readn < 0 && err2 != nil {       fmt.Println("socket read err: ", err2.Error())       break     }   }   // 7. close   _ = syscall.Close(acceptFd)   _ = syscall.Close(socketFd) }

Client：echoClient.go
/** * File: echoClient.go * Author: 蛇叔 * 公众号: 蛇叔编程心法 */ package main import (     "bufio"     "fmt"     "net"     "os"     "syscall" ) const (     PORT = 8888     ADDR = "127.0.0.1"     SIZE = 100 ) func main() {     // 1. 建立socket     socketFd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_STREAM, 0)     if err != nil || socketFd < 0 {         fmt.Println("socket create err: ", err)         os.Exit(-1)     }     ip4 := net.ParseIP(ADDR).To4()     if ip4 == nil {         fmt.Println("net.ParseIP err")         os.Exit(-1)     }     sa := &syscall.SockaddrInet4{Port:PORT}     copy(sa.Addr[:], ip4)     // 2. 发起主动连接     err = syscall.Connect(socketFd, sa)     if err != nil {         fmt.Println("socket connect err: ", err)         os.Exit(-1)     }     var (         bufReader = bufio.NewReader(os.Stdin)         buf = make([]byte, SIZE)         writen int         readn int         err2 error     )     for {         // 3. 从标准输入读取数据         line, _, err := bufReader.ReadLine()         if err != nil {             fmt.Println("bufReader.ReadLine err: ", err)             break         }         buf = line[:]         // 4. 向socket对端写入数据         writen, err2 = syscall.Write(socketFd, buf)         if writen > 0 {             readn, err2 =syscall.Read(socketFd, buf)             if readn > 0 {                 fmt.Println("read from socket: ")                 fmt.Println(string(buf[:readn]))             } else {                 break             }         } else if writen <= 0 && err2 != nil {             fmt.Printf("socket write; writen:%d,  err: %s\n", writen, err2)             break         }     }     // 5. close socketFd     _ = syscall.Close(socketFd) }

jackXiang@localhost  ~/golearning  ./echoClient
jack
read from socket:
jack
xiang
read from socket:
xiang

Q:果然Ok，两个问题探讨下：
1）        ip4 := net.ParseIP(ADDR).To4()
        sa := &syscall.SockaddrInet4{Port: PORT}
        copy(sa.Addr[:], ip4)  #这个sa.Addr[:] 冒号啥写法呢？

2）for { 这里面是epoll 吗？}

A:
1.
copy(sa.Addr[:], ip4)  #这个sa.Addr[:] 冒号啥写法呢？

sa.Addr 是一个数组，
sa.Addr[:] 将这个数组临时转为切片，底层数组指向sa.Addr数组
方便copy进行切片复制

2. 就是个for{}死循环，防止代码往下执行

来自：
https://mp.weixin.qq.com/s/dRADQ5kUCT80dX7oEAAXyA
https://mp.weixin.qq.com/s/kFHw73w_IIqjKeicesCpZw

作者：jackxiang@向东博客 专注WEB应用 构架之美 --- 构架之美，在于尽态极妍 | 应用之美，在于药到病除
地址：http://jackxiang.com/post/10815/
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