Notes

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <errno.h>

#define PORT 4950 /*TCP port for communication*/
#define BUFFER 1024 /*Buffer size used*/

void send_and_recv(int i, int fd)
{
char message[BUFFER]; /*buffer to store the sending messages*/
char reply[BUFFER]; /*buffer to store the messages from other clients*/
int no_bytes; /*number of byte received*/

if (i == 0){ /*indicates the flag which will be set whenever there is data from the other client */
fgets(message, BUFFER, stdin); /*input message*/
if (strcmp(message , "byen") == 0) {/*quit immediately if you client types bye*/
exit(0);
}else
send(fd, message, strlen(message), 0); /*sending message to the server*/
}else {
no_bytes = recv(fd, reply, BUFFER, 0); /*if flag is not set receive the message from other clients through server*/
reply[no_bytes] = '';/*indicating end of message*/
printf("%sn" , reply);/*prints the message*/
fflush(stdout);
}
}


void connect_request(int *fd, struct sockaddr_in *server_addr)
{
if ((*fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {/*creating socket*/
printf("Error in creating Socket");
exit(1);
}
server_addr->sin_family = AF_INET; /*Intiatializing environment for sockaddr structure*/
server_addr->sin_port = htons(PORT);
server_addr->sin_addr.s_addr = inet_addr("127.0.0.1");
memset(server_addr->sin_zero,'', sizeof server_addr->sin_zero);

if(connect(*fd, (struct sockaddr *)server_addr, sizeof(struct sockaddr)) == -1) {/*connecting to the listening server on the port*/
printf("Error while connectingn");
exit(1);
}
}

int main()
{
int fd, maximumfd, i; /*listening socket file descriptor and maximum file descriptor number*/
struct sockaddr_in server_addr; /*sockaddr structure declaration*/
fd_set master; /*master file descriptor set*/
fd_set read_fds; /*list of file descriptor for select*/

connect_request(&fd, &server_addr); /*connection establishment with server*/
FD_ZERO(&master); /*clearing master set*/
FD_ZERO(&read_fds); /*clearing temporary file descriptorr */
FD_SET(0, &master); /*Adding 0 to the master file descriptor*/
FD_SET(fd, &master);/*Adding socket file descriptor to master file descriptor*/
maximumfd = fd; /*Keeping track of maximum file descriptor*/

for(;;){
read_fds = master; /*copy*/
FD_SET(fd,&read_fds);/*Adding socket file descriptor*/
if(select(maximumfd+1, &read_fds, NULL, NULL, NULL) == -1){/*To see the number of file descriptor ready for read*/
printf("None of them are ready");
exit(4);
}

for(i=0; i <= maximumfd; i++ ) /*To keep track of everyone*/
if(FD_ISSET(i, &read_fds))
send_and_recv(i, fd);/*sending data to everyone*/
}
close(fd);
return 0;
}