C - Server broadcasts IP for client - c

Question

I need my server to broadcast a message (not that it matters but it contains its IP/port info). What I have currently is the working server broadcast, code below. I'm not sure about setting up the client because usually I would use the IP/port of the server which the client doesn't have until it receives the broadcast. The client never receives anything. Can someone tell me what is wrong.
Server:
struct sockaddr_in server, bcast;
int sockfd;
int blen = sizeof(bcast);
int svrlen = sizeof(server);
char buf[BUFLEN];
if((sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1){
printf("Socket error.\n");
exit(1);
}
int broadcastPermission = 1;
if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, (void *)&broadcastPermission,sizeof(broadcastPermission)) < 0){
printf("Error setting socket options.");
}
memset(&bcast, 0, sizeof(bcast));
bcast.sin_family = AF_INET;
bcast.sin_port = htons(PORT);
bcast.sin_addr.s_addr = htonl(INADDR_ANY);
string bcastIP = BCASTIP;
if(inet_aton("255.255.255.255", &bcast.sin_addr) == 0){
printf("Broadcast Address error.");
exit(1);
}
if (bind(sockfd, (struct sockaddr*)&server, sizeof(server)) == -1){
printf("Port error.\n");
exit(1);
}
fflush(stdout);
if(int bytes = sendto(sockfd, ipinfo, sizeof(ipinfo), 0, (struct sockaddr*)&bcast, blen) == -1){
printf("Broadcast send error.");
}
else{
printf("Sent"):
}
Client:
struct sockaddr_in server;
int sockfd;
int bytes;
int svrlen = sizeof(server);
char buf[BUFLEN]
if((sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1){
printf("Socket error.\n");
exit(1);
}
memset((char *)&server, 0, sizeof(server));
server.sin_family = AF_INET;
server.sin_port = htons(BPORT);
server.sin_addr.s_addr = htonl(INADDR_ANY);
while(1){
printf("Waiting for broadcast...\n\n");
fflush(stdout);
memset(buf,0,BUFLEN);
bytes = recvfrom(sockfd, buf, BUFLEN, 0, (struct sockaddr*)&server, (socklen_t*)&svrlen);
printf("Received");
}

Answer 1

Your client is not calling bind() on the socket before trying to receive data.
http://cs.baylor.edu/~donahoo/practical/CSockets/code/BroadcastReceiver.c shows the following example which you may find helpful:
void DieWithError(char *errorMessage); /* External error handling function */
int main(int argc, char *argv[])
{
int sock; /* Socket */
struct sockaddr_in broadcastAddr; /* Broadcast Address */
unsigned short broadcastPort; /* Port */
char recvString[MAXRECVSTRING+1]; /* Buffer for received string */
int recvStringLen; /* Length of received string */
if (argc != 2) /* Test for correct number of arguments */
{
fprintf(stderr,"Usage: %s <Broadcast Port>\n", argv[0]);
exit(1);
}
broadcastPort = atoi(argv[1]); /* First arg: broadcast port */
/* Create a best-effort datagram socket using UDP */
if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
DieWithError("socket() failed");
/* Construct bind structure */
memset(&broadcastAddr, 0, sizeof(broadcastAddr)); /* Zero out structure */
broadcastAddr.sin_family = AF_INET; /* Internet address family */
broadcastAddr.sin_addr.s_addr = htonl(INADDR_ANY); /* Any incoming interface */
broadcastAddr.sin_port = htons(broadcastPort); /* Broadcast port */
/* Bind to the broadcast port */
if (bind(sock, (struct sockaddr *) &broadcastAddr, sizeof(broadcastAddr)) < 0)
DieWithError("bind() failed");
/* Receive a single datagram from the server */
if ((recvStringLen = recvfrom(sock, recvString, MAXRECVSTRING, 0, NULL, 0)) < 0)
DieWithError("recvfrom() failed");
recvString[recvStringLen] = '\0';
printf("Received: %s\n", recvString); /* Print the received string */
close(sock);
exit(0);
}

Answer 2

I need my server to broadcast a message (not that it matters but it contains its IP/port info).
That sounds a lot like service discovery. You should really use the standard mDNS/Zeroconf protocol for that. You can use the Avahi library for that (or use the Avahi service on Linux or Zeroconf on MacOS X).