1. The Server Code (server.cpp)

The server "listens" for an incoming connection. Once a client connects, it enters a loop where it first receives a message and then sends a response back.

C++

#include <iostream>

#include <string.h>

#ifdef _WIN32

#include <winsock2.h>

#include <ws2tcpip.h>

#pragma comment(lib, "ws2_32.lib")

#else

#include <sys/socket.h>

#include <arpa/inet.h>

#include <unistd.h>

#define SOCKET int

#define INVALID_SOCKET -1

#define SOCKET_ERROR -1

#define closesocket close

#endif

int main() {

#ifdef _WIN32

WSADATA wsaData;

WSAStartup(MAKEWORD(2, 2), &wsaData);

#endif

SOCKET server_fd = socket(AF_INET, SOCK_STREAM, 0);

sockaddr_in address;

address.sin_family = AF_INET;

address.sin_addr.s_addr = INADDR_ANY;

address.sin_port = htons(8080);

bind(server_fd, (struct sockaddr*)&address, sizeof(address));

listen(server_fd, 3);

std::cout << "Server listening on port 8080...\n";

SOCKET new_socket = accept(server_fd, NULL, NULL);

char buffer[1024] = {0};

const char* server_msg = "Hello from Server!";

// 1. Receive from Client

recv(new_socket, buffer, 1024, 0);

std::cout << "Client says: " << buffer << std::endl;

// 2. Send to Client

send(new_socket, server_msg, strlen(server_msg), 0);

std::cout << "Response sent.\n";

closesocket(new_socket);

closesocket(server_fd);

#ifdef _WIN32

WSACleanup();

#endif

return 0;

}

2. The Client Code (client.cpp)

The client initiates the connection. In this flow, it sends a message first and then waits for the serverâ€™s reply.

C++

#include <iostream>

#include <string.h>

#ifdef _WIN32

#include <winsock2.h>

#include <ws2tcpip.h>

#pragma comment(lib, "ws2_32.lib")

#else

#include <sys/socket.h>

#include <arpa/inet.h>

#include <unistd.h>

#define SOCKET int

#define INVALID_SOCKET -1

#define closesocket close

#endif

int main() {

#ifdef _WIN32

WSADATA wsaData;

WSAStartup(MAKEWORD(2, 2), &wsaData);

#endif

SOCKET sock = socket(AF_INET, SOCK_STREAM, 0);

sockaddr_in serv_addr;

serv_addr.sin_family = AF_INET;

serv_addr.sin_port = htons(8080);

// Use "127.0.0.1" for same machine, or server's IP for different machines

inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr);

if (connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {

std::cout << "Connection Failed\n";

return -1;

}

const char* client_msg = "Hello from Client!";

char buffer[1024] = {0};

// 1. Send to Server

send(sock, client_msg, strlen(client_msg), 0);

std::cout << "Message sent to server.\n";

// 2. Receive from Server

recv(sock, buffer, 1024, 0);

std::cout << "Server replied: " << buffer << std::endl;

closesocket(sock);

#ifdef _WIN32

WSACleanup();

#endif

return 0;

}

Fernando Graham

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