Data exchange between Clients in UDP

Hello

Here the program echos the same messages which was sent by the client to the the same client. I want to interchange the data between clients. for example if two clients are client0, client1. what ever client 1 sends should be echoed to client 0 and similarly what ever client 0 sends should be echoed to client 1. Thank you.

Code:

#include <stdio.h> #include <string.h> //strlen #include <stdlib.h> #include <errno.h> #include <unistd.h> //close #include <arpa/inet.h> //close #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <sys/time.h> //FD_SET, FD_ISSET, FD_ZERO macros #define TRUE 1 #define FALSE 0 #define PORT 1901 int main(int argc , char *argv[]) { int opt = TRUE; int master_socket , addrlen , new_socket , client_socket[2] , max_clients = 2 , activity, i , valread , sd; int max_sd; int port_array[30]; struct sockaddr_in address; char buffer[1025]; //data buffer of 1K //set of socket descriptors fd_set readfds; //a message char *message = "ECHO Daemon v1.0 \r\n"; //initialise all client_socket[] to 0 so not checked for (i = 0; i < max_clients; i++) { client_socket[i] = 0; } //create a master socket if( (master_socket = socket(AF_INET , SOCK_STREAM , 0)) == 0) { perror("socket failed"); exit(EXIT_FAILURE); } //set master socket to allow multiple connections , this is just a good habit, it will work without this if( setsockopt(master_socket, SOL_SOCKET, SO_REUSEADDR, (char *)&opt, sizeof(opt)) < 0 ) { perror("setsockopt"); exit(EXIT_FAILURE); } //type of socket created address.sin_family = AF_INET; address.sin_addr.s_addr = inet_addr("192.168.37.129"); address.sin_port = htons( PORT ); //bind the socket to localhost port 8888 if (bind(master_socket, (struct sockaddr *)&address, sizeof(address))<0) { perror("bind failed"); exit(EXIT_FAILURE); } printf("Listener on port %d \n", PORT); //try to specify maximum of 3 pending connections for the master socket if (listen(master_socket, 3) < 0) { perror("listen"); exit(EXIT_FAILURE); } //accept the incoming connection addrlen = sizeof(address); puts("Waiting for connections ..."); while(TRUE) { //clear the socket set FD_ZERO(&readfds); //add master socket to set FD_SET(master_socket, &readfds); max_sd = master_socket; //add child sockets to set for ( i = 0 ; i < max_clients ; i++) { //socket descriptor sd = client_socket[i]; //if valid socket descriptor then add to read list if(sd > 0) FD_SET( sd , &readfds); //highest file descriptor number, need it for the select function if(sd > max_sd) max_sd = sd; } //wait for an activity on one of the sockets , timeout is NULL , so wait indefinitely activity = select( max_sd + 1 , &readfds , NULL , NULL , NULL); if ((activity < 0) && (errno!=EINTR)) { printf("select error"); } //If something happened on the master socket , then its an incoming connection if (FD_ISSET(master_socket, &readfds)) { if ((new_socket = accept(master_socket, (struct sockaddr *)&address, (socklen_t*)&addrlen))<0) { perror("accept"); exit(EXIT_FAILURE); } //inform user of socket number - used in send and receive commands printf("New connection , socket fd is %d , ip is : %s , port : %d \n" , new_socket , inet_ntoa(address.sin_addr) , ntohs(address.sin_port)); port_array[i] = ntohs(address.sin_port); //send new connection greeting message if( send(new_socket, message, strlen(message), 0) != strlen(message) ) { perror("send"); } puts("Welcome message sent successfully"); //add new socket to array of sockets for (i = 0; i < max_clients; i++) { //if position is empty if( client_socket[i] == 0 ) { client_socket[i] = new_socket; printf("Adding to list of sockets as %d\n" , i); break; } } } //else its some IO operation on some other socket :) for (i = 0; i < max_clients; i++) { sd = client_socket[i]; if (FD_ISSET( sd , &readfds)) { //Check if it was for closing , and also read the incoming message if ((valread = read( sd , buffer, 1024)) == 0) { //Somebody disconnected , get his details and print getpeername(sd , (struct sockaddr*)&address , (socklen_t*)&addrlen); printf("Host disconnected , ip %s , port %d \n" , inet_ntoa(address.sin_addr) , ntohs(address.sin_port)); //Close the socket and mark as 0 in list for reuse close( sd ); client_socket[i] = 0; } //Echo back the message that came in else { if (client_socket[0]==port_array[0]) { //client 0 talking send to client 1 printf("Sedning message to client 1\n"); if (send(client_socket[1] , buffer , strlen(buffer) , 0 )==-1) { err("send()"); } }else { //client 1 talking send to client 0 printf("Sending message to client 0\n"); if (send(client_socket[0] , buffer , strlen(buffer) , 0 )==-1) { err("send()"); } } } } } } return 0; }