🪴 TJ's Notes 1.0

Computer Networks Lab 3

3 min read

Computer Networks Lab 3

Index

  1. Main note
  2. Objective
  3. Materials and Equipment
  4. Procedure
    1. Setting up the TCP Server
    2. Setting up the TCP Client
    3. Steps
    4. Expected Output
  5. Conclusion
  6. References

Main note

Lab Experiment: Implementing TCP Server and Client in C

Objective

The objective of this lab experiment is to create a TCP server and a TCP client using C language. The client will send a message to the server, which will receive, display, and send the message back to the client.

Materials and Equipment

  • A computer with a C compiler installed (e.g., GCC).
  • Basic knowledge of C programming and networking concepts.

Procedure

1. Setting up the TCP Server

Code: TCPServer.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
 
#define PORT 8080
#define BUFFER_SIZE 1024
 
int main() {
    int server_fd, new_socket;
    struct sockaddr_in address;
    int addrlen = sizeof(address);
    char buffer[BUFFER_SIZE] = {0};
    
    // Creating socket file descriptor
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("Socket failed");
        exit(EXIT_FAILURE);
    }
 
    // Forcefully attaching socket to the port 8080
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(PORT);
 
    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
        perror("Bind failed");
        close(server_fd);
        exit(EXIT_FAILURE);
    }
    if (listen(server_fd, 3) < 0) {
        perror("Listen failed");
        close(server_fd);
        exit(EXIT_FAILURE);
    }
    if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) {
        perror("Accept failed");
        close(server_fd);
        exit(EXIT_FAILURE);
    }
    read(new_socket, buffer, BUFFER_SIZE);
    printf("Message received: %s\n", buffer);
    send(new_socket, buffer, strlen(buffer), 0);
    printf("Message sent: %s\n", buffer);
 
    close(new_socket);
    close(server_fd);
    return 0;
}

2. Setting up the TCP Client

Code: TCPClient.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
 
#define PORT 8080
#define BUFFER_SIZE 1024
 
int main() {
    int sock = 0;
    struct sockaddr_in serv_addr;
    char *hello = "Hello from client";
    char buffer[BUFFER_SIZE] = {0};
 
    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("\n Socket creation error \n");
        return -1;
    }
 
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);
 
    if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) {
        printf("\nInvalid address/ Address not supported \n");
        return -1;
    }
 
    if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
        printf("\nConnection Failed \n");
        return -1;
    }
    send(sock, hello, strlen(hello), 0);
    printf("Message sent: %s\n", hello);
    read(sock, buffer, BUFFER_SIZE);
    printf("Message received: %s\n", buffer);
 
    close(sock);
    return 0;
}

Steps

  1. Compile the Server and Client Programs

    gcc TCPServer.c -o TCPServer
gcc TCPClient.c -o TCPClient

  2. Run the Server

    ./TCPServer

  3. Run the Client

    ./TCPClient

Expected Output

  • When the client sends a message, the server will receive and display the message.
  • The server will then send the same message back to the client.
  • The client will display the received message.

Example Output:

Server Side:

Message received: Hello from client
Message sent: Hello from client

Client Side:

Message sent: Hello from client
Message received: Hello from client

Conclusion

In this lab experiment, we successfully implemented a TCP server and client in C. The client sends a message to the server, which then displays and sends the message back to the client. This experiment demonstrates the basics of socket programming and inter-process communication over a network.

References

References

Information
  • date: 2024.07.29
  • time: 10:23](<## Lab Experiment: Implementing TCP Server and Client in C

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