i am trying to make a program where i have a server with multiple clients, where a client sends a message to the server and when the server replies to it, the server broadcasts the reply to all the clients.
the code has some error and is not working.
i turned off my firewall. it is still not helping.
the code for my program is:

server:

#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() */
#include<sys/types.h>
#include<netdb.h>
#include<netinet/in.h>


void DieWithError(char *errorMessage);  /* External error handling function */
void DieWithError(char *errorMessage)
{
    perror(errorMessage);
    exit(1);
}

int main(int argc, char *argv[])
{
        int sock;                         /* Socket */
    int s,n;
        struct sockaddr_in broadcastAddr,client,server; /* Broadcast address */
        char *broadcastIP,b1[100];                /* 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");

    s=socket(AF_INET,SOCK_DGRAM,0);
    server.sin_family=AF_INET;
        server.sin_port=2000;
        server.sin_addr.s_addr=inet_addr("127.0.0.1");

        bind(s,(struct sockaddr *)&server,sizeof(server));
        printf("\nServer ready,waiting for client....\n");


    /* 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 */
    int conn;
        while(1)
        {    unsigned int size = sizeof (client);
        printf("About recv a  datagram\n");
        n=sizeof(client);
        recvfrom(s,b1,sizeof(b1),0,(struct sockaddr *) &client,&n);
        conn=accept(s, (struct sockaddr *) &client, &size);
        read(conn, b1, sizeof(b1) - 1);
            printf("the client sent:: %s \n",b1);

        printf("the code after displaying client side!\n\n");
        printf("ur brooadcast msg:: ");
        scanf("%s",sendString);
            sendStringLen = strlen(sendString);  /* Find length of sendString */
            printf("the expected string length is %d", sendStringLen);


         /* Broadcast sendString in datagram to clients every 3 seconds*/
                sendto(sock, sendString, sendStringLen, 0, (struct sockaddr *)&broadcastAddr, sizeof(broadcastAddr));
           //  DieWithError("sendto() sent a different number of bytes than expected ");


                sleep(3);   /* Avoids flooding the network */

     }
    /* NOT REACHED */
}

the code for client is:

#include <stdio.h> /* for printf() and fprintf() */
#include <sys/socket.h> /* for socket(), connect(), sendto(), and recvfrom() */
#include <arpa/inet.h> /* for sockaddr_in and inet_addr() */
#include <stdlib.h> /* for atoi() and exit() */
#include <string.h> /* for memset() */
#include <unistd.h> /* for close() */
#include<sys/types.h>
#include<netdb.h>
#include<netinet/in.h>

#define MAXRECVSTRING 255 /* Longest string to receive */

void DieWithError(char *errorMessage); /* External error handling function */

void DieWithError(char *errorMessage)
{
    perror(errorMessage);
    exit(1);
}

int main(int argc, char *argv[])
{
    int sock; /* Socket */
    int s,n;
    char b2[100];
    struct sockaddr_in broadcastAddr,client,server; /* 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");

    s=socket(AF_INET,SOCK_DGRAM,0);
    server.sin_family=AF_INET;
        server.sin_port=2000;
        server.sin_addr.s_addr=inet_addr("127.0.0.1");

    /* 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");

    while(1)
    {
        n=sizeof(client);
        printf("\nenter what u wanna send\n");
        fflush(stdin);
        fgets(b2, 20, stdin);

        printf("the entered string is %s", b2);
        sendto(s,b2,strlen(b2),0,(struct sockaddr *) &client,n);

            printf("message sent\n");   

        /* 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);
}

kindly help me with making this code work.
thanks a lot.

Some one basically had the same question in this forum 1 week ago. Search the forum 1st, as it might already has answer to your question. Anyway here is the link to it.

and beej's guide to network programming is the standard for linux sys, if you follow that you should be good.

This article has been dead for over six months. Start a new discussion instead.