Building a Simple TCP Web Client in C

Introduction

In this post, we'll walk through building a simple TCP web client from scratch. Instead of posting the entire code upfront, we'll dive straight into the important sections, explaining the key concepts step by step.

Below here I have shown pseudo code for entire thing

// Import libraries for networking and error handling
// Set buffer size for response data
// Define function to handle errors and exit
// Check if correct arguments (IP & port) are provided
// Set up socket to connect using IP and port
// Try connecting to the server
// Send an HTTP GET request to the server
// Receive and print the response from the server
// Close the socket connection

Part of code Now I want to show is

... includes and Function Prototypes ...

int main(int argc, char *argv[])
{
    .....
    int socket_file_descriptor = socket(AF_INET, SOCK_STREAM, 0);
    if (socket_file_descriptor < 0)
    {
        error_exit("Socket creation failed");
    }
    .....
    close(socket_file_descriptor);
    return 0;
}

void error_exit(const char *message)
{
    perror(message);
    exit(EXIT_FAILURE);
}

• socket() is a system call that creates a new socket for network communication.

• AF_INET specifies that we're using the IPv4 protocol.

• SOCK_STREAM tells the system we're creating a TCP connection (as opposed to a UDP connection).

• The last parameter (0) specifies the protocol to be used (here, the default TCP/IP stack).

• If socket() returns a negative value (usually -1), it means the socket creation failed due to some error (like insufficient resources, invalid arguments, etc.).

Questions that came to my mind

• What other socket types can you create besides SOCK_STREAM?

• What are the other address families available besides AF_INET (IPv4)?

• What are the different protocols you can specify when creating a socket?

Stay tuned as we dive deeper into networking :)