package broadcast
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import (
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"fmt"
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"github.com/gogf/greuse"
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"strconv"
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"strings"
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"sync"
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"time"
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)
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var (
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port = 31995
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lport = 31996
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lock sync.Mutex //同一时刻只能有一个线程在执行搜索
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)
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//广播收集其他节点信息
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func BroadCast() ([]string, error) {
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lock.Lock()
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defer lock.Unlock()
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retCh := make(chan []string)
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go startRecv(retCh)
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conn, err := greuse.Dial("udp", "0.0.0.0:"+strconv.Itoa(lport), "255.255.255.255:"+strconv.Itoa(port))
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if err != nil {
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fmt.Println("err:", err)
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} else {
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defer conn.Close()
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n,err := conn.Write([]byte("who are you?"))
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if err != nil || n == 0 {
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fmt.Println("conn.Write err:", err, " n:", n)
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}
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}
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nodes := <-retCh
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return nodes, nil
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}
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func startRecv(rCh chan []string) {
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conn, err := greuse.ListenPacket("udp", "0.0.0.0:"+strconv.Itoa(lport))
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if err != nil {
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fmt.Println("startRecv ListenPacket err:", err)
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rCh <- []string{}
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return
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}
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//10秒钟之内收到的返回，即认为是在线的
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conn.SetReadDeadline(time.Now().Add(time.Second * 1))
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ch := time.After(time.Second * 4)
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var nodes []string
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Loop:
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for {
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select {
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case <-ch:
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fmt.Println("<-ch")
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break Loop
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default:
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ret := make([]byte, 1024)
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n, from, e := conn.ReadFrom(ret)
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if e == nil && n >0 {
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arr := strings.Split(from.String(), ":")
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if len(arr) == 2 {
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nodes = append(nodes, arr[0])
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}
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fmt.Println("read message from udp:", string(ret), " from:", from)
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} else {
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time.Sleep(time.Millisecond * 100)
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}
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}
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}
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rCh <- nodes
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}
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