I'm writing a program to fetch a udp server. When i first fetch the server it works.

我正在编写一个程序来获取UDP服务器。当我第一次获取服务器时，它可以工作。

But when i input the program second time. This gives me this error

但当我第二次输入程序时。这给了我这个错误

panic: Listen failed:dial udp :8829->:9781: bind: address already in use

Code:

代码：

package main

import (
    "fmt"
    "log"
    "net"
    "os"
)

func main() {
    log.SetFlags(log.Lshortfile)
    udpServer, err := net.ResolveUDPAddr("udp", ":9781")

    if err != nil {
        panic(fmt.Sprint("ResolveUDPAddr failed:", err.Error()))
        os.Exit(1)
    }

    client, err := net.ResolveUDPAddr("udp", ":8829")
    if err != nil {
            panic(err)
    }

    for {
        fmt.Printf(">> ")

        var input string
        fmt.Scanf("%s", &input)

        conn, err := net.DialUDP("udp", client, udpServer)
        if err != nil {
            panic(fmt.Sprint("Listen failed:", err.Error()))
            os.Exit(1)
        }

        _, err = conn.Write([]byte(input))
        if err != nil {
            panic(fmt.Sprint("Write data failed:", err.Error()))
            os.Exit(1)
        }

        received := make([]byte, 1024)
        _, err = conn.Read(received)
        if err != nil {
            panic(fmt.Sprint("Read data failed:", err.Error()))
            os.Exit(1)
        }

        fmt.Printf("Response: %s\n", string(received))
    }

}

I think this happens because i'm using the client twice.

我认为发生这种情况是因为我在使用客户端两次。

But why this causes "address already in use"

但是为什么这会导致“地址已在使用”呢？

I'm not re-creating the client.

我不会重新创建客户的。

Solutions I Tried

我尝试过的解决方案

One of the solution could be set client as nil.

其中一个解决方案可以将客户端设置为空。

Setting to nil will generate a random port.

设置为nil将生成随机端口。

But in my case i need fixed port and fixed network address.

但在我的情况下，我需要固定的端口和固定的网络地址。

So that would not be the solution.

因此，这不是解决方案。

Just create the connection before the loop:

只需在循环之前创建连接：

package main

import (
    "fmt"
    "log"
    "net"
    "os"
)

func main() {
    log.SetFlags(log.Lshortfile)
    udpServer, err := net.ResolveUDPAddr("udp", ":9781")

    if err != nil {
        panic(fmt.Sprint("ResolveUDPAddr failed:", err.Error()))
        os.Exit(1)
    }

    client, err := net.ResolveUDPAddr("udp", ":8829")
    if err != nil {
            panic(err)
    }

    conn, err := net.DialUDP("udp", client, udpServer)
    if err != nil {
        panic(fmt.Sprint("Listen failed:", err.Error()))
        os.Exit(1)
    }

    for {
        fmt.Printf(">> ")

        var input string
        fmt.Scanf("%s", &input)

        _, err = conn.Write([]byte(input))
        if err != nil {
            panic(fmt.Sprint("Write data failed:", err.Error()))
            os.Exit(1)
        }

        received := make([]byte, 1024)
        _, err = conn.Read(received)
        if err != nil {
            panic(fmt.Sprint("Read data failed:", err.Error()))
            os.Exit(1)
        }

        fmt.Printf("Response: %s\n", string(received))
    }

}