In-depth understanding of Socket sockets: detailed explanation of necessary parameters

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In-depth understanding of Socket sockets: detailed explanation of necessary parameters

introduction

1.1 Introduction

Socket Socket is a communication mechanism commonly used in network programming. It can transmit and receive data between different hosts. This article will delve into the necessary parameters of the Socket socket, including the parameters that need to be passed in when creating the socket, as well as the specific meaning and usage of these parameters.

1.2 The role of Socket socket

In network communication, Socket serves as a bridge connecting two hosts. It allows two-way data transmission between hosts, enabling network applications to implement real-time communication, file transfer and other functions.

Creation of Socket

2.1 Socket function

In C language, you can use the Socket function to create a socket. The prototype of this function is as follows:

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

2.2 Detailed explanation of Socket function parameters

domain: specifies the protocol family, common ones include AF_INET (IPv4), AF_INET6 (IPv6) and AF_UNIX (local communication), etc.
type: Specifies the socket type. Common ones include SOCK_STREAM (connection-oriented socket) and SOCK_DGRAM (connection-less socket).
protocol: Specify the protocol, common ones include IPPROTO_TCP (TCP protocol) and IPPROTO_UDP (UDP protocol), etc.

Socket parameters

3.1 Domain (protocol family)

In the Socket function, the domain parameter is used to specify the protocol family. Common protocol families include:

AF_INET: IPv4 protocol suite, used for Internet communication.
AF_INET6: IPv6 protocol suite, used to support more IP addresses.
AF_UNIX: Local communication protocol family, used for inter-process communication.

3.2 Type (socket type)

In the Socket function, the type parameter is used to specify the socket type. Common socket types include:

SOCK_STREAM: Connection-oriented socket, providing reliable, ordered, byte stream-based data transmission.
SOCK_DGRAM: A connectionless socket that provides unreliable, out-of-order, datagram-based data transmission.

3.3 Protocol

In the Socket function, the protocol parameter is used to specify the specific protocol. Common agreements include:

IPPROTO_TCP: TCP protocol, providing reliable, connection-oriented data transmission.
IPPROTO_UDP: UDP protocol, providing unreliable, connectionless data transmission.

3.4 Address

In Socket programming, you need to specify an address for the socket. The structure and configuration method of the address vary according to different protocol families.

Example demonstration

4.1 TCP socket

Here is a sample code using a TCP socket:

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>

int main() {
    
    
    int sockfd;
    struct sockaddr_in server_addr;

    // 创建套接字
    sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (sockfd < 0) {
    
    
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    // 配置服务器地址
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    server_addr.sin_addr.s_addr = INADDR_ANY;

    // 连接服务器
    if (connect(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
    
    
        perror("connection failed");
        exit(EXIT_FAILURE);
    }

    // 发送数据
    char message[] = "Hello, Server!";
    send(sockfd, message, sizeof(message), 0);

    // 接收数据
    char buffer[1024];
    memset(buffer, 0, sizeof(buffer));
    recv(sockfd, buffer, sizeof(buffer), 0);

    printf("Server response: %s\n", buffer);

    // 关闭套接字
    close(sockfd);

    return 0;
}

In the above code, we first socketcreate a TCP socket using the function. We then configured the server's address and used connectthe function to connect to the server. Next, we send a message to the server and recvreceive the server's response using a function. Finally, we close the socket.

4.2 UDP socket

Here is a sample code using a UDP socket:

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>

int main() {
    
    
    int sockfd;
    struct sockaddr_in server_addr;

    // 创建套接字
    sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sockfd < 0) {
    
    
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    // 配置服务器地址
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    server_addr.sin_addr.s_addr = INADDR_ANY;

    // 发送数据
    char message[] = "Hello, Server!";
    sendto(sockfd, message, sizeof(message), 0, (struct sockaddr *)&server_addr, sizeof(server_addr));

    // 接收数据
    char buffer[1024];
    memset(buffer, 0, sizeof(buffer));
    socklen_t addr_len = sizeof(server_addr);
    recvfrom(sockfd, buffer, sizeof(buffer), 0, (struct sockaddr *)&server_addr, &addr_len);

    printf("Server response: %s\n", buffer);

    // 关闭套接字
    close(sockfd);

    return 0;
}

In the above code, we also use socketthe function to create a UDP socket. Then, we configured the server's address and used sendtothe function to send a message to the server. Next, we recvfromreceived the response from the server using a function. Finally, we close the socket.

Frequently Asked Questions

5.1 What are the default values of parameters when creating a Socket socket?

When using socketa function to create a socket, if no parameters are specified, their default values are as follows:

domain: AF_INET (IPv4 protocol family)
type: SOCK_STREAM (connection-oriented socket)
protocol: 0 (the system selects the appropriate protocol)

5.2 How to choose the appropriate protocol family, socket type and protocol?

When selecting protocol families, socket types, and protocols, you need to consider actual needs and application scenarios. Generally speaking:

If reliable, connection-oriented data transmission is required, the TCP protocol and SOCK_STREAM socket should be selected.
If fast, connectionless data transfer is required, the UDP protocol and SOCK_DGRAM socket should be selected.
If local communication is required, you can choose the AF_UNIX protocol family.

in conclusion

This article provides an in-depth analysis of the necessary parameters of the Socket socket, including the parameters that need to be passed in when creating the socket, as well as the specific meaning and usage of these parameters. Through practical examples, readers can more clearly understand the parameter selection and configuration of Socket sockets. At the same time, this article also answers some common questions to help readers better apply Socket sockets.

By studying this article, readers will be able to deeply understand the parameters of Socket sockets, and be able to choose the appropriate protocol family, socket type and protocol according to actual needs. This will provide a more accurate and efficient solution for network programming.

references

Stevens, WR, Fenner, B., & Rudoff, AM (2004). UNIX Network Programming Volume 1: Socket Networking API (3rd Edition). Electronic Industry Press.
Beej, J. (2016). Beej’s Guide to Network Programming. Retrieved from https://beej.us/guide/bgnet/