How to use C++ for network programming?

With the development of the Internet, network programming has increasingly become an important part of computer science. As a powerful programming language, C also provides a lot of support for network programming. This article will introduce how to use C for network programming.

Overview of Network Programming

Network programming refers to the process of writing programs for communication using computer networks. Network programming requires the use of network protocols (such as TCP/IP) for data transmission. In network programming, there are two main roles: client and server. The client refers to the program that initiates the request, while the server is the program that responds to the request and provides data.

C Network Programming

C provides some libraries and tools to support network programming. The following are some commonly used C network programming libraries:

1. Boost.Asio: This is a cross-platform C library for asynchronous and synchronous programming, supporting multiple network protocols, including TCP/IP, UDP and SSL.
2. Poco C: This is a cross-platform C class library for developing network-based applications, supporting protocols such as HTTP, SMTP and POP3.
3. ACE: This is an object-level network programming toolkit based on C language, supporting asynchronous I/O, multiplexing and distributed applications, etc.

In this article, we will mainly introduce how to use the socket library in the C standard library for network programming.

Use the C socket library for network programming

In C, the socket library is one of the important libraries used for network programming. The socket library provides an easy, portable way to communicate between remote computers, allowing programmers to quickly create network applications.

Before using the socket library, you need to include the following header files:

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#include <iostream>
#include <stdlib.h>

Create socket

To create a C socket, you can use the socket() function, the code is as follows:

int sockfd = socket(AF_INET, SOCK_STREAM, 0);

Here, AF_INET indicates the use of IPv4 protocol, SOCK_STREAM indicates the use of TCP protocol for transmission, and 0 indicates the use of the default protocol.

Connect to the server

If you want to connect to the server, you can use the connection command to achieve it. When used on the client, after using the socket() function to create the socket, you can use the connection function connect() to bind the socket to the server. The code is as follows:

struct sockaddr_in serv_addr;
memset(&serv_addr, '0', sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(port);
if (inet_pton(AF_INET, ip, &serv_addr.sin_addr) <= 0)
{
    std::cerr << "Error: Address not supported" << std::endl;
    return -1;
}

if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
{
    std::cerr << "Error: Connection Failed" << std::endl;
    return -1;
}

Here, the IP address and port number of the server must be specified. The inet_pton() function converts a standard dotted decimal IP address into network byte order. If the connection fails, -1 will be returned.

Sending and receiving data

You can use the send() and recv() functions to send and receive data. The following is the code to send data:

int bytes_sent = send(sockfd, buffer, strlen(buffer), 0);

Here, sockfd is the socket, buffer is the data to be sent, strlen(buffer) is the length of the data, and 0 means no flag is set.

The following is the code to receive data:

char incoming_buffer[1024];
memset(incoming_buffer, '0', sizeof(incoming_buffer));
bytes_received = recv(sockfd, incoming_buffer, 1024, 0);
std::cout << "Received: " << incoming_buffer << std::endl;

Here, incoming_buffer is a character array of size 1024, the recv() function will read the data from the connected socket and convert it Stored in incoming_buffer.

Close the connection

When you finish sending and receiving data, you need to close the connection through the close() function. The code is as follows:

close(sockfd);

This will close the connection socket and release related resources.

Summary

In this article, we introduced how to use C’s socket library for network programming. Basic network programming involves creating sockets, connecting to servers, sending and receiving data, and closing connections. In actual network application development, you may need to handle more situations, such as handling multiple connections, using non-blocking sockets, and so on. However, we believe that what has been mentioned here already provides a good starting point for beginners.

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