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BroadcastSender.c
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BroadcastSender.c
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#include <stdio.h> /* for printf() and fprintf() */
#include <sys/socket.h> /* for socket() and bind() */
#include <arpa/inet.h> /* for sockaddr_in */
#include <stdlib.h> /* for atoi() and exit() */
#include <string.h> /* for memset() */
#include <unistd.h> /* for close() */
void DieWithError(char *errorMessage); /* External error handling function */
int main(int argc, char *argv[])
{
int sock; /* Socket */
struct sockaddr_in broadcastAddr; /* Broadcast address */
char *broadcastIP; /* IP broadcast address */
unsigned short broadcastPort; /* Server port */
char *sendString; /* String to broadcast */
int broadcastPermission; /* Socket opt to set permission to broadcast */
unsigned int sendStringLen; /* Length of string to broadcast */
if (argc < 4) /* Test for correct number of parameters */
{
fprintf(stderr,"Usage: %s <IP Address> <Port> <Send String>\n", argv[0]);
exit(1);
}
broadcastIP = argv[1]; /* First arg: broadcast IP address */
broadcastPort = atoi(argv[2]); /* Second arg: broadcast port */
sendString = argv[3]; /* Third arg: string to broadcast */
/* Create socket for sending/receiving datagrams */
if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
DieWithError("socket() failed");
/* Set socket to allow broadcast */
broadcastPermission = 1;
if (setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (void *) &broadcastPermission,
sizeof(broadcastPermission)) < 0)
DieWithError("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(broadcastIP);/* Broadcast IP address */
broadcastAddr.sin_port = htons(broadcastPort); /* Broadcast port */
sendStringLen = strlen(sendString); /* Find length of sendString */
for (;;) /* Run forever */
{
/* Broadcast sendString in datagram to clients every 3 seconds*/
if (sendto(sock, sendString, sendStringLen, 0, (struct sockaddr *)
&broadcastAddr, sizeof(broadcastAddr)) != sendStringLen)
DieWithError("sendto() sent a different number of bytes than expected");
sleep(3); /* Avoids flooding the network */
}
/* NOT REACHED */
}