client.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

#define PORT 8080
#define MAX_BUFFER_SIZE 1024

int main() {
    int client_socket;
    struct sockaddr_in server_addr;
    char buffer[MAX_BUFFER_SIZE];

    // Create a socket
    if ((client_socket = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        perror("Error creating socket");
        exit(EXIT_FAILURE);
    }
    
    // Set up the server address
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    server_addr.sin_port = htons(PORT);

    if (connect(client_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
        perror("Error connecting to server");
        close(client_socket);
        exit(EXIT_FAILURE);
    }

    // Send a message to the server
    const char *message = "Hello, Echo Server!";
    write(client_socket, message, strlen(message));

    // Receive and print the echoed message from the serve
    ssize_t bytes_received = read(client_socket, buffer, sizeof(buffer));
    if (bytes_received == -1){
        perror("Error reading from server");
    } else {
        buffer[bytes_received] = '\0';
        printf("Received from server: %s\n", buffer);
    }

    close(client_socket);

    return 0;
}   

CMakeLists.txt

# CMakeLists.txt

cmake_minimum_required(VERSION 3.10)
project(EchoServerClient)

# Server executable
add_executable(server server.c)

# Client executable
add_executable(client client.c)

Makefile

CC = gcc
CFLAGS = -Wall -Wextra

all: server client

server: server.c
	$(CC) $(CFLAGS) -o server server.c

client: client.c
	$(CC) $(CFLAGS) -o client client.c

.PHONY: clean run_server run_client

clean:
	rm -f server client

run_server: server
	./server

run_client: client
	./client

server.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

#define PORT 8080
#define MAX_BUFFER_SIZE 1024

int main() {
    int server_socket, client_socket;
    struct sockaddr_in server_addr, client_addr;
    socklen_t client_addr_len = sizeof(client_addr);
    char buffer[MAX_BUFFER_SIZE];

    // Create a socket
    if ((server_socket = socket(AF_INET, SOCK_STREAM, 0)) == -1){
        perror("Error creating socket");
        exit(EXIT_FAILURE);
    }

    // Set up the server address
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(PORT);

    // Bind the socket to the specified address and port
    if (bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
        perror("Error binding socket");
        close(server_socket);
        exit(EXIT_FAILURE);
    }

    // Listen for incoming connections
    if (listen(server_socket, 5) == -1) {
        perror("Error listening for connections");
        close(server_socket);
        exit(EXIT_FAILURE);
    }

    printf("Server listening on port %d...\n", PORT);

    // Accept and handle incoming connections
    while (1){
        // Accept a connection
        if ((client_socket = accept(server_socket, (struct sockaddr*)&client_addr, &client_addr_len)) == -1){
            perror("Error accepting connection");
            continue;
        }

        printf("Accepted connection from %s\n", inet_ntoa(client_addr.sin_addr));
        
        // Receive and echo data
        ssize_t bytes_received;
        while ((bytes_received = read(client_socket, buffer, sizeof(buffer))) > 0) {
            // Echo back the received data
            write(client_socket, buffer, bytes_received);
        }

        if (bytes_received == -1) {
            perror("Error reading from client");
        }

        // Close the client socket
        close(client_socket);
        printf("Connection closed\n");

    }

    // Close the server socket (this part will not be reached in this example)
    close(server_socket);

    return 0;
}

Usage.md

Usage

To run the build the program you can use CMAKE or Make.

Using Make

Running the following commands

make all
make run_server  # Run this in one terminal
make run_client  # Run this in another terminal

Using CMake

Create a build directory:

mkdir build
cd build

Run the command below from within the build directory:

cmake ..

This will make your Makefile then build your project by running the command below:

make

This will create the executables.

Run the server executable:

./server

Open another terminal and run the client executable:

./client