func serve(addr string)  {
    address, err := net.ResolveUDPAddr("udp", addr)
    if err != nil {
        fmt.Printf("resolve udp service address: %v failed, error: %v", addr, err.Error())
        return 
    }
    udpConn, err := net.ListenUDP("udp", address)
    if err != nil {
        fmt.Printf("listen udp address: %v failed, error: %v", address.String(), err.Error())
        return
    }
	// 获取文件描述符
    fd, err := udpConn.File()
    if err != nil {
       fmt.Printf("get udp conn file err: %v \n", err)
       return
    }
    defer fd.Close()
    oriUdpSocketBufferSize, err := syscall.GetsockoptInt(int(fd.Fd()), syscall.SOL_SOCKET, unix.SO_RCVBUF)
    fmt.Printf("get opt int fd recv buf size: %v \n", oriUdpSocketBufferSize)
    
    fmt.Printf("udp server create success \n")

    go func() {
       buf := make([]byte, 1024)
       for {
           n, caddr, err := udpConn.ReadFrom(buf)
           if err != nil {
               fmt.Println("read failed", err)
               continue
           }
           fmt.Println(addr, caddr, string(buf[:n]))
       }
    }()

    time.Sleep(2*time.Second)

    go func() {
       err := udpConn.Close()
       if err != nil {
           fmt.Printf("udp conn close err: %v \n", err)
           return
       }
       _, err = net.ListenUDP("udp", address)
       if err != nil {
           fmt.Printf("listen udp address: %v failed, error: %v \n", address.String(), err.Error())
       }
       fmt.Printf("repeat listen udp success")
    }()
}

func main() {
    go serve("127.0.0.1:1234")
    select {}
}