练习 8.4: 修改reverb2服务器,在每一个连接中使用sync.WaitGroup来计数活跃的echo goroutine。当计数减为零时,关闭TCP连接的写入,像练习8.3中一样。验证一下你的修改版netcat3客户端会一直等待所有的并发“喊叫”完成,即使是在标准输入流已经关闭的情况下。
重点:等待所有的goroutine执行完成后再关闭TCP连接
package main
import (
"bufio"
"fmt"
"log"
"net"
"strings"
"time"
"sync"
)
func main() {
listener, err := net.Listen("tcp", ":8040")
if err != nil {
log.Fatal(err)
}
for {
conn, err := listener.Accept()
if err != nil {
log.Print(err) // e.g., connection aborted
continue
}
go handleConn(conn) //新建goroutines处理连接
}
}
func handleConn(c net.Conn) {
input := bufio.NewScanner(c)
var wg sync.WaitGroup
//var ch =make(chan struct{})
for input.Scan() {
wg.Add(1)
go func(c net.Conn, shout string, delay time.Duration) {
defer wg.Done()
fmt.Fprintln(c, "\t", strings.ToUpper(shout))
time.Sleep(delay)
fmt.Fprintln(c, "\t", shout)
time.Sleep(delay)
fmt.Fprintln(c, "\t", strings.ToLower(shout))
//ch<-struct{}{}
}(c, input.Text(), 1*time.Second)
}
wg.Wait()
//cw := c.(*net.TCPConn)
//cw.CloseWrite()
c.Close()
}