Address Stucture for recvfrom vs. sendto

[kardon33]

Is there a difference between the way the function recvfrom and sendto use the address structure.

When i use sento it works fine, but when I try and use recvfrom with the same variables it errors out with (bad address).

Or is there a better way to receive packets from a socket that i just sent to.

Theres some of my source code.

 
    struct sockaddr_in a;
      a.sin_family = AF_INET;
      a.sin_addr.s_addr = htonl(INADDR_ANY);
      a.sin_port = htons(DefaultPort);
      int sock;
      sock = socket(AF_INET, SOCK_DGRAM, 0);  
 
      int fBroadcast = 1;
      int err = setsockopt(sock, SOL_SOCKET, SO_BROADCAST, "C", 5);
      if (err == -1) { perror("setsockopt");     exit(1); }        
 
      //Binding the address to the socket
      err = bind(sock, (struct sockaddr *)&a, sizeof(a));
      if (err == -1) { perror("bind"); exit(1); }    
 
 
      //Putting the ip address in the socket output address structure
      a.sin_addr.s_addr = inet_addr(ip);
 
 
      //Sending the information to the specified port
      if (sendto(sock, packet, len, 0,    (struct sockaddr *)&a, sizeof(a)) == -1)
      { perror("sendto"); exit(1);  }
 
      int rcv;
      char buf[300];
 
       // Recieve
      rcv = recvfrom(sock, buf, 208, MSG_WAITALL, (struct sockaddr *)&a , sizeof(a));
    if(rcv == -1) { perror("recvfrom"); exit(1); }  
 
 

[weaknessforcats]

The variable a is a struct sockaddr_in.

You typecast the address of a to a struct sockaddr*.

The only way this will work is if struct sockaddr_in and struct sockaddr have the same members and each member has the same size.

Otherwise, you can't make a struct sockaddr out of a struct sockaddr_in just by typecasting an address.

[thespartan]

Hi kardon33, did you find out the cause of the error. I also face same problem. The sendto with similar signature is able to send out packets, but recvfrom throws bad address, any one ideas?