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?