协议UDP -C不支持的地址族

Question

我正在尝试创建一个UDP交互客户机/服务器。我在试图用这段代码发送消息时遇到了一些问题。在执行过程中，我得到了以下错误：

sendto函数之后的"Address族不受协议支持“。提前感谢！

int prepare_udp_socket(char *pong_addr, char *pong_port)
{
    struct addrinfo gai_hints, *pong_addrinfo = NULL;
    int ping_socket;
    int gai_rv;
    int np;

            /*** Specify the UDP sockets' options ***/
            memset(&gai_hints, 0, sizeof gai_hints);
            gai_hints.ai_family=AF_INET;
            gai_hints.ai_socktype=SOCK_DGRAM;
            gai_hints.ai_flags=0;
            gai_hints.ai_protocol = IPPROTO_UDP;

            if ((ping_socket = socket(gai_hints.ai_family, gai_hints.ai_socktype, gai_hints.ai_protocol)) == -1)
                fail_errno("UDP Ping could not get socket");
            /*** change socket behavior to NONBLOCKING ***/
            if(fcntl(ping_socket,F_SETFL, O_NONBLOCK)==-1)
                fail_errno("set NONBLOCKING socket fail");

            //call getaddrinfo() in order to get Pong Server address in binary form 
            gai_rv=getaddrinfo(pong_addr, pong_port, &gai_hints, &pong_addrinfo);

            if(gai_rv!=0){
                printf("Getaddrinfo failed\n");
                exit(1);
            }   
            /*** connect the ping_socket UDP socket with the server ***/    
        if(connect(ping_socket, pong_addrinfo->ai_addr, pong_addrinfo->ai_addrlen)!=0){
              fail_errno("Can't connect");
            }     
            freeaddrinfo(pong_addrinfo);
            return ping_socket;
        }

    double do_ping(int msg_size, int msg_no, char message[msg_size], int ping_socket, double timeout)
    {
        int lost_count = 0;
        char answer_buffer[msg_size];
        ssize_t recv_bytes, sent_bytes;
        int offset;
        struct sockaddr_storage pong_addr;
        size_t pong_addr_len = sizeof(struct sockaddr_storage);
        struct timespec send_time, recv_time;
        double roundtrip_time_ms;
        int re_try = 0;
        /*** write msg_no at the beginning of the message buffer ***/
    if(sprintf(message,"%d\n",msg_no)<0){
            fail("sprintf(...) failed");
        }
        do {
            debug(" ... sending message %d\n", msg_no);
        /*** Store the current time in send_time ***/
        if(clock_gettime(CLOCK_MONOTONIC,&send_time)!=0){
          fail_errno("clock_gettime failed with sendTime");
        }
        /*** Send the message through the socket ***/
        **if((sent_bytes = sendto(ping_socket, &message, msg_size,0,(struct sockaddr*)&pong_addr,pong_addr_len)) == -1){
            fail_errno("Cannot send bytes throught the socket");**
        }

Answer 1

问题是在您的do_ping函数中，sendto期望地址和长度作为其第5个和第6个参数，它们是输入参数，这意味着您需要指定要将数据包发送到的目标主机的地址，必须将地址初始化为有效的地址。实际上，你正在做的事情就像'recvfrom`‘。

另外，message是指向函数内char的指针，所以不要在sendto中使用&message，只需传递message。

struct sockaddr_storage pong_addr;
// pong_addr is not initialized here, initialize pong_addr to a valid address, like the one you got from `getaddrinfo` call
size_t pong_addr_len = sizeof(struct sockaddr_storage);

// then call sendto to send to the address
if((sent_bytes = sendto(ping_socket, message, msg_size, 0, (struct sockaddr*)&pong_addr, pong_addr_len)) == -1){
    fail_errno("Cannot send bytes throught the socket");**
}