golang 的 net 库为什么接不到其他 tcp 消息？

以下是一个 go 教程的聊天服务器例子，例子的 S 端 C 端都没问题。为什么我用网络调试助手 tcp client 可以连上，但是发信息收不到呢？我在 S 端的很多位置都 fmt.Println 了都找不到。

//以下是服务端 // Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan. // License: creativecommons.org/licenses/by-nc-sa/4.0/ // See page 254. //!+ // Chat is a server that lets clients chat with each other. package main

import ( "bufio" "fmt" "log" "net" )

//!+broadcaster type client chan<- string // an outgoing message channel

var ( entering = make(chan client) leaving = make(chan client) messages = make(chan string) // all incoming client messages )

func broadcaster() { clients := make(map[client]bool) // all connected clients for { select { case msg := <-messages: // Broadcast incoming message to all // clients' outgoing message channels.

		for cli := range clients {
			cli <- msg
			fmt.Println(msg)
		}

	case cli := <-entering:
		clients[cli] = true

	case cli := <-leaving:
		delete(clients, cli)
		close(cli)
	}
}

}

//!-broadcaster

//!+handleConn func handleConn(conn net.Conn) { ch := make(chan string) // outgoing client messages go clientWriter(conn, ch)

who := conn.RemoteAddr().String()
ch <- "You are " + who
messages <- who + " has arrived"
entering <- ch

input := bufio.NewScanner(conn)
for input.Scan() {
	messages <- who + ": " + input.Text()
	fmt.Println(222)
}
// NOTE: ignoring potential errors from input.Err()

leaving <- ch
messages <- who + " has left"
conn.Close()

}

func clientWriter(conn net.Conn, ch <-chan string) { for msg := range ch { fmt.Fprintln(conn, msg) // NOTE: ignoring network errors } }

//!-handleConn

//!+main func main() { listener, err := net.Listen("tcp", "localhost:8000") if err != nil { log.Fatal(err) }

go broadcaster()
for {
	conn, err := listener.Accept()
	fmt.Println(111)
	if err != nil {
		log.Print(err)
		continue
	}
	go handleConn(conn)
}

} //!-main

//以下是客户端 // Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan. // License: creativecommons.org/licenses/by-nc-sa/4.0/ // See page 227. // Netcat is a simple read/write client for TCP servers. package main

import ( "io" "log" "net" "os" )

//!+ func main() { conn, err := net.Dial("tcp", "localhost:8000") if err != nil { log.Fatal(err) } done := make(chan struct{}) go func() { io.Copy(os.Stdout, conn) // NOTE: ignoring errors log.Println("done") done <- struct{}{} // signal the main goroutine }() mustCopy(conn, os.Stdin) conn.Close() <-done // wait for background goroutine to finish }

//!-

func mustCopy(dst io.Writer, src io.Reader) { if _, err := io.Copy(dst, src); err != nil { log.Fatal(err) } }