C 中的 UDP 套接字 - Sendto() 发送失败：参数无效

Question

我正在尝试以非常简单/基本的方式在 C 中实现 UDP 套接字。我的程序旨在在终端之间发送/接收文件，每个终端上运行一个程序。我的客户端代码中的 sendto() 函数有问题。这是我的代码：

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<arpa/inet.h>
#include<sys/socket.h>
#include <errno.h>

#define BUFFER_SIZE 512

int main(int argc, char *argv[])
{
    struct sockaddr_in client;
    int sockfd, bytes, errno, slen = sizeof(client);
    char buffer[BUFFER_SIZE];

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    if(sockfd == -1)
    {
        perror("Socket creation failed.");
        return 0;
    }

    client.sin_addr.s_addr = INADDR_ANY;
    client.sin_family = AF_INET;
    client.sin_port = htons( 0 );

    if( bind(sockfd, (struct sockaddr *)&client, sizeof(client)) == -1)
    {
        perror("Bind call failed.");
        return 0;
    }

    while(1)
    {
        printf("Enter message : ");
        fgets(buffer, BUFFER_SIZE, stdin);

        printf("Message: %s\n", buffer);
        bytes = sendto(sockfd, buffer, strlen(buffer), 0, (struct sockaddr *)&client, sizeof(client));

        printf("Bytes: %d\n", bytes);

        if(bytes == -1)
        {
            printf("Error number: %d", errno);
            perror("Send failed.");
            return 0;
        }

        memset(buffer,'\0', BUFFER_SIZE);

        if( recvfrom(sockfd, buffer, BUFFER_SIZE, 0, (struct sockaddr *)&client, &slen) == -1)
        {
            perror("Recieve failed.");
            return 0;
        }

        puts(buffer);
    }

    close(sockfd);

    return 0;   
}

无论我在缓冲区中输入什么，我总是会从 sendto() 中得到错误号 22 的无效参数。我已经尝试了所有遇到的解决方案或调整，但似乎没有任何效果。

Answer 1

只要在bind()后面加上这段代码

getsockname(sockfd, (struct sockaddr *)&client, &slen);

手册页

 DESCRIPTION
     The getsockname() function returns the current address for the specified
     socket.

     The address_len parameter should be initialized to indicate the amount of
     space pointed to by address.  On return it contains the actual size of
     the address returned (in bytes).

     The address is truncated if the buffer provided is too small.

RETURN VALUES
     The getsockname() function returns the value 0 if successful; otherwise
     the value -1 is returned and the global variable errno is set to indicate
     the error.