加入upnp多播组(239.255.255.250:1900)

golang的udp组播， 如果你家里有路由器，可以试一下。

package main

import (
    "bufio"
    "bytes"
    "log"
    "net"
    "net/http"
    "regexp"
)

func handler(r *http.Request) {
    log.Printf("Got %s %s message from %v: %v", r.Method, r.URL.Path, r.RemoteAddr, r.Header)
}

var (
    trailingWhitespaceRx = regexp.MustCompile(" +\r\n")
    crlf                 = []byte("\r\n")
)

// 加入upnp多播组: 239.255.255.250:1900
func main() {
    var addr *net.UDPAddr
    var err error

    if addr, err = net.ResolveUDPAddr("udp", "239.255.255.250:1900"); err != nil {
        log.Fatal(err)
    }

    var conn net.PacketConn

    // net.Interface is nil, call net.joinIPv4Group
    if conn, err = net.ListenMulticastUDP("udp", nil, addr); err != nil {
        log.Fatal(err)
    }

    log.Println("begin to receive: ")
    buf := make([]byte, 2048)

    for {
        n, peerAddr, err := conn.ReadFrom(buf[0:])
        log.Println("n=", n)
        if err != nil {
            log.Fatal(err)
            break
        }

        reqbytes := buf[:n]
        reqbytes = trailingWhitespaceRx.ReplaceAllLiteral(reqbytes, crlf)

        req, err := http.ReadRequest(bufio.NewReader(bytes.NewBuffer(reqbytes)))
        if err != nil {
            log.Printf("Failed to parse request: %v", err)
            return
        }
        req.RemoteAddr = peerAddr.String()
        handler(req)
    }
}