Server implementation of client-server chat using Winsock

server.cpp

#include <winsock2.h>
#include <iostream>

struct CLIENT_INFO {
    SOCKET hClientSocket;
    struct sockaddr_in clientAddr;
};

char szServerIPAddr[] = "192.168.1.4";     // Put here the IP address of the server
int nServerPort = 5050;                    // The server port that will be used by
// clients to talk with the server

bool InitWinSock2_0();

BOOL WINAPI ClientThread(LPVOID lpData);

using namespace std;

int main() {
    if (!InitWinSock2_0()) {
        cout << "Unable to Initialize Windows Socket environment" << WSAGetLastError() << endl;
        return -1;
    }

    SOCKET hServerSocket;

    hServerSocket = socket(
            AF_INET,        // The address family. AF_INET specifies TCP/IP
            SOCK_STREAM,    // Protocol type. SOCK_STREM specified TCP
            0               // Protoco Name. Should be 0 for AF_INET address family
    );
    if (hServerSocket == INVALID_SOCKET) {
        cout << "Unable to create Server socket" << endl;
        // Cleanup the environment initialized by WSAStartup()
        WSACleanup();
        return -1;
    }

    // Create the structure describing various Server parameters
    struct sockaddr_in serverAddr;

    serverAddr.sin_family = AF_INET;     // The address family. MUST be AF_INET
    serverAddr.sin_addr.s_addr = inet_addr(szServerIPAddr);
    serverAddr.sin_port = htons(nServerPort);

    // Bind the Server socket to the address & port
    if (bind(hServerSocket, (struct sockaddr *) &serverAddr, sizeof(serverAddr)) == SOCKET_ERROR) {
        cout << "Unable to bind to " << szServerIPAddr << " port " << nServerPort << endl;
        // Free the socket and cleanup the environment initialized by WSAStartup()
        closesocket(hServerSocket);
        WSACleanup();
        return -1;
    }

    // Put the Server socket in listen state so that it can wait for client connections
    if (listen(hServerSocket, SOMAXCONN) == SOCKET_ERROR) {
        cout << "Unable to put server in listen state" << endl;
        // Free the socket and cleanup the environment initialized by WSAStartup()
        closesocket(hServerSocket);
        WSACleanup();
        return -1;
    }

    // Start the infinite loop
    while (true) {
        // As the socket is in listen mode there is a connection request pending.
        // Calling accept( ) will succeed and return the socket for the request.
        SOCKET hClientSocket;
        struct sockaddr_in clientAddr;
        int nSize = sizeof(clientAddr);

        hClientSocket = accept(hServerSocket, (struct sockaddr *) &clientAddr, &nSize);
        if (hClientSocket == INVALID_SOCKET) {
            cout << "accept( ) failed" << endl;
        } else {
            HANDLE hClientThread;
            struct CLIENT_INFO clientInfo;
            DWORD dwThreadId;

            clientInfo.clientAddr = clientAddr;
            clientInfo.hClientSocket = hClientSocket;

            cout << "Client connected from " << inet_ntoa(clientAddr.sin_addr) << endl;

            // Start the client thread
            hClientThread = CreateThread(NULL, 0,
                                         (LPTHREAD_START_ROUTINE) ClientThread,
                                         (LPVOID) &clientInfo, 0, &dwThreadId);
            if (hClientThread == NULL) {
                cout << "Unable to create client thread" << endl;
            } else {
                CloseHandle(hClientThread);
            }
        }
    }

    closesocket(hServerSocket);
    WSACleanup();
    return 0;
}

bool InitWinSock2_0() {
    WSADATA wsaData;
    WORD wVersion = MAKEWORD(2, 0);

    return !WSAStartup(wVersion, &wsaData);
}

BOOL WINAPI ClientThread(LPVOID lpData) {
    CLIENT_INFO *pClientInfo = (CLIENT_INFO *) lpData;
    char szBuffer[1024];
    int nLength;

    while (1) {
        nLength = recv(pClientInfo->hClientSocket, szBuffer, sizeof(szBuffer), 0);
        if (nLength > 0) {
            szBuffer[nLength] = '\0';
            cout << "Received " << szBuffer << " from " << inet_ntoa(pClientInfo->clientAddr.sin_addr) << endl;

            // Convert the string to upper case and send it back, if its not QUIT
            strupr(szBuffer);
            if (strcmp(szBuffer, "QUIT") == 0) {
                closesocket(pClientInfo->hClientSocket);
                return TRUE;
            }
            // send( ) may not be able to send the complete data in one go.
            // So try sending the data in multiple requests
            int nCntSend = 0;
            char *pBuffer = szBuffer;

            while ((nCntSend = send(pClientInfo->hClientSocket, pBuffer, nLength, 0) != nLength)) {
                if (nCntSend == -1) {
                    cout << "Error sending the data to " << inet_ntoa(pClientInfo->clientAddr.sin_addr) << endl;
                    break;
                }
                if (nCntSend == nLength)
                    break;

                pBuffer += nCntSend;
                nLength -= nCntSend;
            }
        } else {
            cout << "Error reading the data from " << inet_ntoa(pClientInfo->clientAddr.sin_addr) << endl;
        }
    }

    return TRUE;
}

Hi, Thanks a lot for sharing!

Shouldn't it be

nLength = recv(pClientInfo->hClientSocket, szBuffer, sizeof(szBuffer) - 1, 0);

(reducing the number of bytes to read by -1) in line 115 (https://gist.github.com/redatawfik/78caa1d6e06ebc0b94125c9b47183003#file-server-cpp-L115)?

Wouldn't otherwise szBuffer[nLength] = '\0' (line 117) throw, if the full buffer has been filled?

Thanks and best,
Mo