golang TCPConn.setwritedadline不'；似乎没有如预期的那样工作

我试图通过检查golang返回的错误来检测发送失败，但结果为零。我也尝试过使用，但没有成功

事情就是这样发生的：

服务器启动

客户端连接

服务器发送消息，客户端接收消息

客户端关闭

服务器再发送一条消息：无错误

服务器发送第三条消息：只是现在出现错误

问题：为什么只有发送给不存在的客户端的第二条消息会导致错误？如何妥善处理

守则如下：

package main

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

func AcceptConnections(listener net.Listener, console <- chan string) {

    msg := ""

    for {

        conn, err := listener.Accept()

        if err != nil {
            panic(err)
        }

        fmt.Printf("client connected\n")

        for {

            if msg == "" {
                msg = <- console
                fmt.Printf("read from console: %s", msg)
            }

            err = conn.SetWriteDeadline(time.Now().Add(time.Second))

            if err != nil {
                fmt.Printf("SetWriteDeadline failed: %v\n", err)
            }

            _, err = conn.Write([]byte(msg))

            if err != nil {
                // expecting an error after sending a message
                // to a non-existing client endpoint
                fmt.Printf("failed sending a message to network: %v\n", err)
                break
            } else {
                fmt.Printf("msg sent: %s", msg)
                msg = ""
            }
        }
    }
}

func ReadConsole(network chan <- string) {

    console := bufio.NewReader(os.Stdin)

    for {

        line, err := console.ReadString('\n')

        if err != nil {

            panic(err)

        } else {

            network <- line
        }
    }
}

func main() {

    listener, err := net.Listen("tcp", "localhost:6666")

    if err != nil {
        panic(err)
    }

    println("listening on " + listener.Addr().String())

    consoleToNetwork := make(chan string)

    go AcceptConnections(listener, consoleToNetwork)

    ReadConsole(consoleToNetwork)
}

客户端如下所示：

listening on 127.0.0.1:6666
client connected
hi there!
read from console: hi there!
msg sent: hi there!
this one should fail
read from console: this one should fail
msg sent: this one should fail
this one actually fails
read from console: this one actually fails
failed sending a message to network: write tcp 127.0.0.1:51194: broken pipe

package main

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

func cp(dst io.Writer, src io.Reader, errc chan<- error) {

    // -reads from src and writes to dst
    // -blocks until EOF
    // -EOF is not an error
    _, err :=  io.Copy(dst, src)

    // push err to the channel when io.Copy returns
    errc <- err
}

func StartCommunication(conn net.Conn) {

    //create a channel for errors
    errc := make(chan error)

    //read connection and print to console
    go cp(os.Stdout, conn, errc)

    //read user input and write to connection
    go cp(conn, os.Stdin, errc)

    //wait until nil or an error arrives
    err := <- errc

    if err != nil {
        println("cp error: ", err.Error())
    }
}

func main() {

    servAddr := "localhost:6666"

    tcpAddr, err := net.ResolveTCPAddr("tcp", servAddr)

    if err != nil {
        println("ResolveTCPAddr failed:", err.Error())
        os.Exit(1)
    }

    conn, err := net.DialTCP("tcp", nil, tcpAddr)

    if err != nil {
        println("net.DialTCP failed:", err.Error())
        os.Exit(1)
    }

    defer conn.Close()

    StartCommunication(conn)

}

主程序包
进口(
“净额”
“操作系统”
“io”
//“布菲奥”
//“fmt”
)
func cp（dst io.Writer、src io.Reader、errc chan这不是特定的，而是底层TCP套接字的产物

TCP终止步骤的示意图位于本页底部：

简单的版本是，当客户端关闭其套接字时，它会发送一个FIN，并从服务器接收一个ACK。然后，它会等待服务器执行相同的操作。但是，您不会发送FIN，而是发送更多的数据，这些数据会被丢弃，客户端套接字现在假定来自您的任何更多数据都是无效的，因此下次发送时你会得到一个RST，这就是你所看到的错误

回到您的程序，您需要以某种方式处理此问题。通常，您可以想到谁负责发起发送，谁也负责发起终止，因此您的服务器应该假定它可以继续发送，直到关闭连接或遇到错误。如果您需要更可靠地检测客户端closing，您需要在协议中有某种客户端响应。这样，可以在套接字上调用recv并返回0，这会提醒您连接已关闭

在go中，这将从连接的读取方法（或在您的情况下从副本中）返回EOF错误.SetWriteDeadline不起作用，因为一个小的写操作将被执行并以静默方式删除，或者客户端最终将以RST响应，从而给您一个错误。
最好回答您自己的问题，而不是编辑问题以包含答案
package main

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

type Connection struct {
    IsFaulted bool
    Conn net.Conn
}

func StartWritingToNetwork(connWrap * Connection, errChannel chan <- error, msgStack chan string) {

    for {

        msg := <- msgStack

        if connWrap.IsFaulted {

            //put it back for another connection
            msgStack <- msg

            return
        }

        _, err := connWrap.Conn.Write([]byte(msg))

        if err != nil {

            fmt.Printf("failed sending a message to network: %v\n", err)

            connWrap.IsFaulted = true

            msgStack <- msg

            errChannel <- err

            return

        } else {

            fmt.Printf("msg sent: %s", msg)
        }
    }
}

func StartReadingFromNetwork(connWrap * Connection, errChannel chan <- error){

    network := bufio.NewReader(connWrap.Conn)

    for (!connWrap.IsFaulted) {

        line, err := network.ReadString('\n')

        if err != nil {

            fmt.Printf("failed reading from network: %v\n", err)

            connWrap.IsFaulted = true

            errChannel <- err

        } else {

            fmt.Printf("%s", line)
        }
    }
}

func AcceptConnections(listener net.Listener, console chan string) {

    errChannel := make(chan error)

    for {

        conn, err := listener.Accept()

        if err != nil {
            panic(err)
        }

        fmt.Printf("client connected\n")

        connWrap := Connection{false, conn}

        go StartReadingFromNetwork(&connWrap, errChannel)

        go StartWritingToNetwork(&connWrap, errChannel, console)

        //block until an error occurs
        <- errChannel
    }
}

func ReadConsole(network chan <- string) {

    console := bufio.NewReader(os.Stdin)

    for {

        line, err := console.ReadString('\n')

        if err != nil {

            panic(err)

        } else {

            network <- line
        }
    }
}

func main() {

    listener, err := net.Listen("tcp", "localhost:6666")

    if err != nil {
        panic(err)
    }

    println("listening on " + listener.Addr().String())

    consoleToNetwork := make(chan string)

    go AcceptConnections(listener, consoleToNetwork)

    ReadConsole(consoleToNetwork)
}