global table of clients C : Chatroom - c

Question

I created a client/server chatroom in C. I need to put in a global table of all clients connected so that I can send every message the server receives to all the clients connected. I can't figure out how to do this. I assume I have to create a struct of some sort and add every specific socket descriptor for each thread I spawn. Then I have to send my message to every specific SD in that struct.
I don't know how to code this and wanted to see if anyone could show me some example code of what I have to write after every connection is made and what I have to write to then send my messages to every thread. My server code is below if needed.
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <sys/socket.h>
#include <unistd.h>
#include <string.h>
#include <malloc.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <errno.h>
#include <netdb.h>
#include <sys/stat.h>
#include <fcntl.h>
void *
client_session_thread(void * arg)
{
int SD;
char request[2048];
char message[2048] = "server receives input: ";
int chatfile;
char msgr[50000];
SD = *(int *)arg;
free (arg);
pthread_detach(pthread_self());
chatfile = open("chathistory.txt", O_RDWR|O_CREAT|O_EXCL,0666);
close(chatfile);
chatfile = open("chathistory.txt", O_RDWR | O_APPEND);
read(chatfile,msgr,sizeof(msgr));
write(SD, msgr, strlen(msgr));
while (read(SD, request, sizeof(request)))
{
strcat(message, request);
strcat(message,"\n");
fprintf(stdout, message);
write(SD,request,strlen(request));
write(chatfile,request,strlen(request));
strcpy(request,"");
strcpy(message, "server receives input: ");
bzero(request, sizeof(request));
bzero(message,sizeof(message));
}
close(SD);
close(chatfile);
return 0;
}
int main(int argc, char *argv[])
{
//create a socket. SD is my socket.
struct addrinfo addrinfo;
struct addrinfo * result;
char message[256];
int SD;
int FD;
pthread_t ignore;
int * FDpntr;
int on = 1;
addrinfo.ai_flags = 0;
addrinfo.ai_family = AF_INET; // IPv4 only
addrinfo.ai_socktype = SOCK_STREAM; // Want TCP/IP
addrinfo.ai_protocol = 0; // Any protocol
addrinfo.ai_addrlen = 0;
addrinfo.ai_addr = NULL;
addrinfo.ai_canonname = NULL;
addrinfo.ai_next = NULL;
if (getaddrinfo("clamshell.rutgers.edu", "5700", &addrinfo, &result) !=0)
{
printf("\x1b[1;31mProblem with getaddrinfo\x1b[0m\n");
}
//Create socket
SD = socket(AF_INET, SOCK_STREAM, 0);
if (SD == -1)
{
printf("\x1b[1;31mProblem creating socket\x1b[0m\n");
}
//Bind the socket to our specified IP and port
if (setsockopt(SD, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) ==-1)
{
printf("\x1b[1;31mProblem with sockopt\x1b[0m\n");
freeaddrinfo(result);
return -1;
}
if (bind(SD, result->ai_addr, result->ai_addrlen) != 0)
{
printf("\x1b[1;31mProblem binding socket\x1b[0m\n");
}
//first we bind our socket and then recast our address just like in client
//Listen function listens for connections
if (listen(SD, 20) == -1)
{
printf("\x1b[1;31mProblem with listen\x1b[0m\n");
close(SD);
return 0;
}
else
{
//Accept function for accepting incoming connection
//sos = sizeof(struct sockaddr_in);
//while (FD = accept(SD, (struct sockaddr *)&client, (socklen_t*)&sos))
while ((FD = accept(SD,0,0)) != -1)
{
FDpntr = (int *)malloc(sizeof(int));
*FDpntr = FD;
if (pthread_create(&ignore, NULL, client_session_thread, FDpntr) != 0)
{
printf("\x1b[1;31mProblem creating thread\x1b[0m\n");
}
else
{
continue;
}
}
close(SD);
return 0;
}
}

Answer 1

suggest implement a separate file.
That file would have entry points:
initializeClientTable()
destroyClientTable()
addClient()
deleteClient(),
getClient()
The getClient() function would return a client.
it would have a parameter that (probably an enum value) that indicates to get the first client or get the next client from the ClientTable
When at the end of the ClientTable, return an indication of such event.
The ClientTable could easily be implemented as a linked list.