c - 在 Linux 中通过套接字发送广播

Question

已解决请关闭问题(但我真的不知道如何:/糟糕的一天)

我试图通过套接字在 linux 中发送广播，它总是通过两个接口(interface)发出(我有事件的 eth0 和 eth1，它们都在不同的网段)，但是突然间，它只通过第一个接口(interface) eth0 发出

代码如下:

void sendBroad(char *dstIP, char *localIP)
{
    int sock;                         /* Socket */
    struct sockaddr_in broadcastAddr; /* Broadcast address */
    int broadcastPermission;          /* Socket opt to set permission to broadcast */
    unsigned int localIPLen;       /* Length of string to broadcast */


    /* Create socket for sending/receiving datagrams */
    if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
        perror("socket() failed");

    /* Set socket to allow broadcast */
    broadcastPermission = 1;
    if (setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (void *) &broadcastPermission, 
          sizeof(broadcastPermission)) < 0)
        perror("setsockopt() failed");

    /* Construct local address structure */
    memset(&broadcastAddr, 0, sizeof(broadcastAddr));   /* Zero out structure */
    broadcastAddr.sin_family = AF_INET;                 /* Internet address family */
    broadcastAddr.sin_addr.s_addr = inet_addr(dstIP);   /* Broadcast IP address */
    broadcastAddr.sin_port = htons(BroadcastPort);      /* Broadcast port */

    localIPLen = strlen(localIP);  /* Find length of localIP */
    int j;
    for (j=0; j<1; j++) //doesnt mean anything so far, not important
    {
         /* Broadcast localIP in datagram to clients */
         if (sendto(sock, localIP, localIPLen, 0, (struct sockaddr *) 
               &broadcastAddr, sizeof(broadcastAddr)) != localIPLen)
             perror("sendto() sent a different number of bytes than expected");


    }
}

对这个问题有帮助吗？

提前致谢!

Answer 1

您的代码乍一看没问题。问题可能出在目标 IP 地址中。

请注意，您是否意识到数据报无论如何都会与其源地址一起到达？您也不需要将地址放入有效负载中。您可以在其中放置更具体的内容，例如应用程序标识符。