func ListenUDP()

in pkg/util/net/udp.go [165:216]
43 lines of code
9 McCabe index (conditional complexity)

func ListenUDP(bindAddr string, bindPort int) (l *UDPListener, err error) {
	udpAddr, err := net.ResolveUDPAddr("udp", net.JoinHostPort(bindAddr, strconv.Itoa(bindPort)))
	if err != nil {
		return l, err
	}
	readConn, err := net.ListenUDP("udp", udpAddr)

	l = &UDPListener{
		addr:      udpAddr,
		acceptCh:  make(chan net.Conn),
		writeCh:   make(chan *UDPPacket, 1000),
		fakeConns: make(map[string]*FakeUDPConn),
	}

	// for reading
	go func() {
		for {
			buf := pool.GetBuf(1450)
			n, remoteAddr, err := readConn.ReadFromUDP(buf)
			if err != nil {
				close(l.acceptCh)
				close(l.writeCh)
				return
			}

			fakeConn, exist := l.fakeConns[remoteAddr.String()]
			if !exist || fakeConn.IsClosed() {
				fakeConn = NewFakeUDPConn(l, l.Addr(), remoteAddr)
				l.fakeConns[remoteAddr.String()] = fakeConn
			}
			fakeConn.putPacket(buf[:n])

			l.acceptCh <- fakeConn
		}
	}()

	// for writing
	go func() {
		for {
			packet, ok := <-l.writeCh
			if !ok {
				return
			}

			if addr, ok := packet.RemoteAddr.(*net.UDPAddr); ok {
				_, _ = readConn.WriteToUDP(packet.Buf, addr)
			}
		}
	}()

	return
}