doutuobao4004 2018-11-15 16:39
浏览 101
已采纳

序列化结构以通过UDP发送

I'm trying to figure out how to serialize a struct and send it via UDP to my server. I managed to actually send the struct but upon receiving I do not have any values in it... Except when I statically add a number.

In the following code I am sending a UDP packet to port 8080 with a sequential number which are just the numbers from 0-9. I'm adding + 1 to it to show my point. What I expect is that on the receiving end I should receive in the message part 1-10. But the only thing I receive is the number 1 which means that the variable should be set to 0.

To verify if I actually send 0 I print the length of the buffer I receive and it is the correct length of what it should be. So I must be doing something wrong with the decoding.

send function:

func send_udp() {
    dst, _ := net.ResolveUDPAddr("udp", "localhost:8080")
    conn, _ := net.ListenPacket("udp", ":0")
    defer conn.Close()

    var buf bytes.Buffer
    encoder := gob.NewEncoder(&buf)
    for n := 0; n < 10; n++ {
        var msg int64 = int64(n) + 1
        packet := &Packet{[]int{5}, msg}
        encoder.Encode(packet)
        conn.WriteTo(buf.Bytes(), dst)
    }
}

The listen function:

func listen_udp() {
    dst, _ := net.ResolveUDPAddr("udp", "localhost:8080")
    conn, _ := net.ListenUDP("udp", dst)
    defer conn.Close()

    for {
        buf := make([]byte, 4096)
        n, _, _ := conn.ReadFromUDP(buf[:])
        fmt.Println(n)
        dec := gob.NewDecoder(bytes.NewReader(buf[:n]))
        p := Packet{}
        dec.Decode(&p)
        if len(p.Parts) != 0 {
            fmt.Printf("Received: %+v
", p)
        }
    }
}

the struct I'm trying to send:

type Packet struct {
    Parts   []int 
    Message int64 
}
  • 写回答

1条回答 默认 最新

  • dqxz96998 2018-11-15 20:20
    关注

    Implemented this on my local machine. Yes PLEASE check your errors, but lucky for you, nothing was returning any. Here is what I did to fix the problem. In send_udp initialize the Buffer and Encoder INSIDE the for loop.

    func send_udp() error {
        dst, err := net.ResolveUDPAddr("udp", "localhost:8080")
        if err != nil {
            return err
        }
        conn, err := net.ListenPacket("udp", ":0")
        if err != nil {
            return err
        }
        defer conn.Close()
    
        for n := 0; n < 10; n++ {
            // inside for loop
            var buf bytes.Buffer
            encoder := gob.NewEncoder(&buf)
    
            var msg int64 = int64(n) + 1
            packet := &Packet{[]int{5}, msg}
            err = encoder.Encode(packet)
            if err != nil {
                return err
            }
            _, err = conn.WriteTo(buf.Bytes(), dst)
            if err != nil {
                return err
            }
        }
        return nil
    }
    

    Note that declaring the Buffer outside the for loop, you were actually sending every previous Packet each time you added a new one, hence the increasing n values when you printed the return from ReadFromUDP in your listen_udp function, but it was only decoding the first one every time. So if you were meaning to send them all at once, you would have to loop over the Decoder in your listen_udp function.

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论

报告相同问题?

悬赏问题

  • ¥15 公交车和无人机协同运输
  • ¥15 stm32代码移植没反应
  • ¥15 matlab基于pde算法图像修复,为什么只能对示例图像有效
  • ¥100 连续两帧图像高速减法
  • ¥15 组策略中的计算机配置策略无法下发
  • ¥15 如何绘制动力学系统的相图
  • ¥15 对接wps接口实现获取元数据
  • ¥20 给自己本科IT专业毕业的妹m找个实习工作
  • ¥15 用友U8:向一个无法连接的网络尝试了一个套接字操作,如何解决?
  • ¥30 我的代码按理说完成了模型的搭建、训练、验证测试等工作(标签-网络|关键词-变化检测)