Go代码epollechoserver代码实现

　　基于 epoll 系统调用实现非阻塞的echo server:
　　这部分代码是 Go BIO/NIO探讨(7)：IO多路复用之epoll 的附录
　　package main  import (   ＂fmt＂   ＂log＂   ＂net＂   ＂os＂   ＂os/signal＂   ＂syscall＂ )  func ipToSockaddrInet4(ip net.IP, port int) (syscall.SockaddrInet4, error) {   if len(ip) == 0 {     ip = net.IPv4zero   }   ip4 := ip.To4()   if ip4 == nil {     return syscall.SockaddrInet4{}, &net.AddrError{Err: ＂non-IPv4 address＂, Addr: ip.String()}   }   sa := syscall.SockaddrInet4{Port: port}   copy(sa.Addr[:], ip4)   return sa, nil }  func isError(ev uint32) bool {   return (ev&uint32(syscall.EPOLLERR)) > 0 || (ev&uint32(syscall.EPOLLHUP)) > 0 || (ev&syscall.EPOLLIN) == 0 }  func main() {   var (     family        = syscall.AF_INET     sotype        = syscall.SOCK_STREAM     _             = ＂tcp＂     listenBacklog = syscall.SOMAXCONN     serverip      = net.IPv4(0, 0, 0, 0)     serverport    = 8080   )    // 创建套接字   sockfd, err := syscall.Socket(family, sotype, 0)   if err != nil {     panic(fmt.Errorf(＂fails to create socket: %s＂, err))   }    syscall.CloseOnExec(sockfd)   // epoll edge-triggered 模式支持nonblock   if err := syscall.SetNonblock(sockfd, true); err != nil {     syscall.Close(sockfd)     panic(fmt.Errorf(＂setnonblock error=%v＂, err))   }    // 接收到Ctrl+C信号后，关闭socket   c := make(chan os.Signal)   signal.Notify(c, os.Interrupt, syscall.SIGTERM)   go func() {     <-c     log.Println(＂r- Ctrl+C pressed in Terminal＂)      if err := syscall.Close(sockfd); err != nil {       log.Printf(＂Close sockfd %d fails, err=%v ＂, sockfd, err)     } else {       log.Printf(＂Server stopped successfully!!!＂)     }     // 收到信号后需要处理, 否则程序会永久hang住, 需要kill -9      // os.Exit 会导致所有goroutine都会立即停止执行     os.Exit(0)   }()    addr, err := ipToSockaddrInet4(serverip, serverport)   if err != nil {     panic(fmt.Sprintf(＂fails to convert address %s:%d to socket addr, err=%s＂, serverip, serverport, err))   }    if err := syscall.Bind(sockfd, &addr); err != nil {     panic(fmt.Sprintf(＂fails to bind socket %d to address %s:%d, err=%s＂,       sockfd,       serverip, serverport,       err))   }    if err := syscall.Listen(sockfd, listenBacklog); err != nil {     log.Printf(＂listen sockfd %d to addr error=%v ＂, sockfd, err)     panic(fmt.Sprintf(＂fails to listen socket %d＂, sockfd))   } else {     log.Printf(＂Started listening on %s:%d＂, serverip, serverport)   }    epfd, err := syscall.EpollCreate1(0)   if err != nil {     panic(fmt.Sprintf(＂create epoll instance fails, err=%s＂, err))   }   // 默认是 level-triggered，效率更高的poll   epEvent := syscall.EpollEvent{     Fd:     int32(sockfd),     Events: uint32(syscall.EPOLLIN) | uint32(-syscall.EPOLLET),   }    if err := syscall.EpollCtl(epfd, syscall.EPOLL_CTL_ADD, sockfd, &epEvent); err != nil {     panic(fmt.Errorf(＂epoll_ctl %v fails, err=%s＂, epfd, err))   }    events := make([]syscall.EpollEvent, 128, 128)   var buf [32 * 1024]byte    for {     // msec < 0, EpollWait 会被阻塞直到有一个 fd 可用     nReady, err := syscall.EpollWait(epfd, events, -1)     if err != nil {       log.Printf(＂epoll_wait error=%v ＂, err)       panic(fmt.Errorf(＂epoll_wait error=%v＂, err))     }      for i := 0; i < nReady; i++ {       ev := &events[i]       if isError(ev.Events) {         /* An error has occured on this fd, or the socket is not            ready for reading (why were we notified then?) */         log.Printf(＂epoll error: %s ＂, err)         // 取消监听         _ = syscall.EpollCtl(epfd, syscall.EPOLL_CTL_DEL, int(ev.Fd), ev)         _ = syscall.Close(int(events[i].Fd))         continue       }        if ev.Fd == int32(sockfd) {         for {           // 监听套接字（server端套接字           clientfd, _, err := syscall.Accept(sockfd)           if err == syscall.EAGAIN || err == syscall.EWOULDBLOCK {             // 所有新创建的tcp conn均已被处理             break           }           // 设置为nonblock           if err := syscall.SetNonblock(clientfd, true); err != nil {             log.Printf(＂fails to set client socket %v as nonblock, err=%s ＂, clientfd, err)             continue           }           epEvent.Fd = int32(clientfd)           epEvent.Events = uint32(syscall.EPOLLIN) | uint32(-syscall.EPOLLET)           if err := syscall.EpollCtl(epfd, syscall.EPOLL_CTL_ADD, clientfd, &epEvent); err != nil {             log.Printf(＂register client socket %v fails, err=%s ＂, clientfd, err)             syscall.Close(clientfd)             continue           }         }       } else {         // 已连接套接字 tcp conn         for {           nRead, err := syscall.Read(int(ev.Fd), buf[:])           if err == syscall.EAGAIN || err == syscall.EWOULDBLOCK {             // 数据已经读完了             break           } else if err != nil {             log.Printf(＂fails to read data from sockfd %d, err=%v ＂, ev.Fd, err)             _ = syscall.EpollCtl(epfd, syscall.EPOLL_CTL_DEL, int(ev.Fd), ev)             _ = syscall.Close(int(ev.Fd))             break           } else if nRead == 0 { // EOF             // Client closed             log.Printf(＂client sock %d closed ＂, ev.Fd)             _ = syscall.EpollCtl(epfd, syscall.EPOLL_CTL_DEL, int(ev.Fd), ev)             _ = syscall.Close(int(ev.Fd))             break           } else {             log.Printf(＂read %d bytes from sock %d ＂, nRead, ev.Fd)             if _, err := syscall.Write(int(ev.Fd), buf[:nRead]); err != nil {               log.Printf(＂fails to write data %s into sockfd %d, err=%v ＂, buf[:nRead], sockfd, err)             }           }         }       }     }   } }