i Have used thread concept to handle multiple connections. But It's not working for multiple clients. please help me

        // Server code
        #undef UNICODE

        #define WIN32_LEAN_AND_MEAN
        #define _WIN32_WINNT 0x501
        #include <windows.h>
        #include <winsock2.h>
        #include <ws2tcpip.h>
        #include <stdlib.h>
        #include <stdio.h>
        #include <pthread.h>
        // Need to link with Ws2_32.lib
        #pragma comment (lib, "Ws2_32.lib")
        // #pragma comment (lib, "Mswsock.lib")

        #define DEFAULT_BUFLEN 512
        #define DEFAULT_PORT "27015"
        void *connection_handler(void *);
        int __cdecl main(void) 
        {
            WSADATA wsaData;
            int iResult, *new_sock;

            SOCKET ListenSocket = INVALID_SOCKET;
            SOCKET ClientSocket = INVALID_SOCKET;

            struct addrinfo *result = NULL;
            struct addrinfo hints;

            int iSendResult;
            char recvbuf[DEFAULT_BUFLEN];
            int recvbuflen = DEFAULT_BUFLEN;

            // Initialize Winsock
            iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
            if (iResult != 0) {
                printf("WSAStartup failed with error: %d\n", iResult);
                return 1;
            }

            ZeroMemory(&hints, sizeof(hints));
            hints.ai_family = AF_INET;
            hints.ai_socktype = SOCK_STREAM;
            hints.ai_protocol = IPPROTO_TCP;
            hints.ai_flags = AI_PASSIVE;

            // Resolve the server address and port
            iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
            if ( iResult != 0 ) {
                printf("getaddrinfo failed with error: %d\n", iResult);
                WSACleanup();
                return 1;
            }

            // Create a SOCKET for connecting to server
            ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
            if (ListenSocket == INVALID_SOCKET) {
                printf("socket failed with error: %ld\n", WSAGetLastError());
                freeaddrinfo(result);
                WSACleanup();
                return 1;
            }

            // Setup the TCP listening socket
            iResult = bind( ListenSocket, result->ai_addr, (int)result->ai_addrlen);
            if (iResult == SOCKET_ERROR) {
                printf("bind failed with error: %d\n", WSAGetLastError());
                freeaddrinfo(result);
                closesocket(ListenSocket);
                WSACleanup();
                return 1;
            }

            //freeaddrinfo(result);

                printf("starting\n");
                iResult = listen(ListenSocket, SOMAXCONN);
                if (iResult == SOCKET_ERROR) {
                    printf("listen failed with error: %d\n", WSAGetLastError());
                    closesocket(ListenSocket);
                    WSACleanup();
                    return 1;
                }

                // Accept a client socket
               while( ClientSocket = accept(ListenSocket, NULL, NULL)) {
                if (ClientSocket == INVALID_SOCKET) {
                    printf("accept failed with error: %d\n", WSAGetLastError());
                    closesocket(ListenSocket);
                    WSACleanup();
                    return 1;
                }

                puts("Connection accepted");

                pthread_t sniffer_thread;
                new_sock = (int*)malloc(1);
                *new_sock = ClientSocket;

                if( pthread_create( &sniffer_thread , NULL ,  connection_handler , (void*) new_sock) < 0)
                {
                    perror("could not create thread");
                    return 1;
                }

                //Now join the thread , so that we dont terminate before the thread
                //pthread_join( sniffer_thread , NULL);
                puts("Handler assigned");
            }

            if (ClientSocket < 0)
            {
                perror("accept failed");
                return 1;
            }

            return 0;
        }
        void *connection_handler(void *socket_desc)
        {
            //Get the socket descriptor
            int sock = *(int*)socket_desc;
            int read_size;
            const char *message ;
            char client_message[2000];

            //Send some messages to the client
            message = "Greetings! I am your connection handler\n";
            send(sock , message , strlen(message),0);

            message = "Now type something and i shall repeat what you type \n";
            send(sock , message , strlen(message),0);

            //Receive a message from client
            while( (read_size = recv(sock , client_message , 2000 , 0)) > 0 )
            {
                //Send the message back to client
                send(sock , client_message , strlen(client_message),0);
            }

            if(read_size == 0)
            {
                puts("Client disconnected");
                fflush(stdout);
            }
            else if(read_size == -1)
            {
                perror("recv failed");
            }

            //Free the socket pointer
            free(socket_desc);

            return 0;
        }

    =======================================================================================================
        // Client code

        #define WIN32_LEAN_AND_MEAN
        #define _WIN32_WINNT 0x501
        #include <windows.h>
        #include <winsock2.h>
        #include <ws2tcpip.h>
        #include <stdlib.h>
        #include <stdio.h>
        #include <string>
        #include <iostream>
        using namespace std;
        // Need to link with Ws2_32.lib, Mswsock.lib, and Advapi32.lib
        #pragma comment (lib, "Ws2_32.lib")
        #pragma comment (lib, "Mswsock.lib")
        #pragma comment (lib, "AdvApi32.lib")

        #define DEFAULT_BUFLEN 512
        #define DEFAULT_PORT "27015"

        int __cdecl main(int argc, char **argv) 
        {
            WSADATA wsaData;
            SOCKET ConnectSocket = INVALID_SOCKET;
            struct addrinfo *result = NULL,
                            *ptr = NULL,
                            hints;
            //const char *sendbuf = "this is a test";
            char recvbuf[DEFAULT_BUFLEN];
            int iResult;
            int recvbuflen = DEFAULT_BUFLEN;

            // Validate the parameters
            if (argc != 2) {
                printf("usage: %s server-name\n", argv[0]);
                return 1;
            }

            // Initialize Winsock
            iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
            if (iResult != 0) {
                printf("WSAStartup failed with error: %d\n", iResult);
                return 1;
            }

            ZeroMemory( &hints, sizeof(hints) );
            hints.ai_family = AF_UNSPEC;
            hints.ai_socktype = SOCK_STREAM;
            hints.ai_protocol = IPPROTO_TCP;

            // Resolve the server address and port
            iResult = getaddrinfo(argv[1], DEFAULT_PORT, &hints, &result);
            if ( iResult != 0 ) {
                printf("getaddrinfo failed with error: %d\n", iResult);
                WSACleanup();
                return 1;
            }

            // Attempt to connect to an address until one succeeds
            for(ptr=result; ptr != NULL ;ptr=ptr->ai_next) {

                // Create a SOCKET for connecting to server
                ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype, 
                    ptr->ai_protocol);
                if (ConnectSocket == INVALID_SOCKET) {
                    printf("socket failed with error: %ld\n", WSAGetLastError());
                    WSACleanup();
                    return 1;
                }

                // Connect to server.
                iResult = connect( ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
                if (iResult == SOCKET_ERROR) {
                    closesocket(ConnectSocket);
                    ConnectSocket = INVALID_SOCKET;
                    continue;
                }
                break;
            }

            while(true){
                printf("Enter message : \n");
                string temp = "";
                cin >> temp;
                strcpy(recvbuf, temp.c_str());

                //Send some data
                if( send(ConnectSocket , recvbuf , strlen(recvbuf) , 0) < 0)
                {
                    printf("Send failed");
                    return 1;
                }
               // printf("client reply :%s ", recvbuf);

                //Receive a reply from the server
                if( recv(ConnectSocket , recvbuf , 2000 , 0) < 0)
                {
                    printf("recv failed");
                    break;
                }

                printf("Server reply :%s \n", recvbuf);

            } 

            // cleanup
            closesocket(ConnectSocket);
            WSACleanup();

            return 0;
        }

First, asking us to analyze over 250 lines of code is just disrespectful. Please indicate what errors you are getting, and where they are coming from at the least.

Sorry I thought I have listed the problems.
1) My problem was that when I connect to client and keep on messaging and suppose a new client connects and exits. I am getting connection reset error from server.
2) suppose I want to send message from one client to another client how do I handle with threads. I need a model. I am already handling multiple Clients.
Thanks in advance :)

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