How do C++ functions establish and manage client sockets in network programming?

To establish and manage client sockets in C, you need to follow the following steps: Use the socket() function to create a socket. Use the connect() function to connect the socket to the server. Use the send() and recv() functions to exchange data with the server.

C function creates and manages client sockets in network programming

Establishes and manages client sockets is a basic task in network programming, and C provides several functions to achieve this goal.

Establish a client socket

Use the socket() function to create a socket:

#include <sys/socket.h>

int socket(int domain, int type, int protocol);

• domain: Specifies the protocol family, usually AF_INET (IPv4) or AF_INET6 (IPv6).
• type: Specifies the socket type, for clients usually use SOCK_STREAM (TCP) or SOCK_DGRAM (UDP).
• protocol: Typically 0, allowing the operating system to choose the default protocol.

Example:

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

Connect to the server

Use the connect() function Connect client socket to server:

#include <sys/socket.h>

int connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen);

• sockfd: Client socket descriptor.
• addr: Server address structure (usually sockaddr_in).
• addrlen: The size of the address structure.

Example:

struct sockaddr_in servaddr;
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(80);
inet_pton(AF_INET, "192.168.1.100", &servaddr.sin_addr);

int rc = connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

Send and receive data

Use send() and recv() functions exchange data with the server:

#include <sys/socket.h>

ssize_t send(int sockfd, const void *buf, size_t len, int flags);
ssize_t recv(int sockfd, void *buf, size_t len, int flags);

• sockfd: Client socket descriptor.
• buf: Data buffer.
• len: The length of data sent or received.
• flags: flag, usually 0.

Example:

char buf[1024];
int n = recv(sockfd, buf, sizeof(buf), 0);

Practical case: Establishing and managing client sockets

This is a A complete C program demonstrating how to use the above functions to establish and manage client sockets:

#include <iostream>
#include <sys/socket.h>
#include <netinet/in.h>

int main() {
    // 创建套接字
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        std::cout << "Error creating socket" << std::endl;
        return -1;
    }

    // 连接到服务器
    struct sockaddr_in servaddr;
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(80);
    inet_pton(AF_INET, "192.168.1.100", &servaddr.sin_addr);
    int rc = connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
    if (rc < 0) {
        std::cout << "Error connecting to server" << std::endl;
        return -1;
    }

    // 发送数据
    const char *msg = "Hello, server!";
    int n = send(sockfd, msg, strlen(msg), 0);
    if (n < 0) {
        std::cout << "Error sending data" << std::endl;
        return -1;
    }

    // 接收数据
    char buf[1024];
    n = recv(sockfd, buf, sizeof(buf), 0);
    if (n < 0) {
        std::cout << "Error receiving data" << std::endl;
        return -1;
    }

    std::cout << "Received data: " << buf << std::endl;

    // 关闭套接字
    close(sockfd);

    return 0;
}

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