5
我試圖通過檢查由golang TCPConn.Write返回的錯誤來檢測發送失敗，但它是零。我也嘗試使用TCPConn.SetWriteDeadline沒有成功。golang TCPConn.SetWriteDeadline似乎沒有按預期工作
這是如何的事情發生了：
- 服務器啓動
- 客戶端連接
- 服務器發送一條消息，客戶端接收它
- 客戶關閉
- 的服務器再發送一條消息：無錯誤
- 服務器發送第三條消息GE：現在纔出現的錯誤
問題：爲什麼只有第二個消息中的錯誤不存在的客戶端的結果嗎？應如何妥善處理案件？
的代碼如下：
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)
}
服務器控制檯看起來是這樣的：
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
客戶看起來是這樣的：
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)
}
編輯：繼JimB的建議，我想出了一個工作的例子。消息不會再丟失，並以新的連接重新發送。我不太清楚在不同的go例程之間使用共享變量（connWrap.IsFaulted）有多安全。
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)
}
最好回答自己的問題，而不是編輯問題以包含答案 – Joakim 2017-10-15 19:53:30