Introduction to common network protocols and functions in the Linux protocol stack

As an open source operating system, Linux’s network protocol stack plays a vital role, responsible for processing network data transmission, routing, connection management and other functions. This article will introduce some common network protocols and their functions in the Linux protocol stack, and attach specific code examples.

1. TCP Protocol

TCP (Transmission Control Protocol) is a connection-oriented, reliable, byte stream-based transmission protocol. It provides data integrity verification, flow control, congestion control and other functions to ensure reliable transmission of data.

The following is a simple example of using the TCP protocol for client-server communication:

// TCP client
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>

int main() {
    int sockfd;
    struct sockaddr_in server_addr;
    char buffer[1024];

    sockfd = socket(AF_INET, SOCK_STREAM, 0);

    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

    connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr));

    send(sockfd, "Hello, server!", strlen("Hello, server!"), 0);

    recv(sockfd, buffer, sizeof(buffer), 0);

    printf("%s
", buffer);

    close(sockfd);

    return 0;
}

// TCP server
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>

int main() {
    int sockfd, client_sock;
    struct sockaddr_in server_addr, client_addr;
    char buffer[1024];

    sockfd = socket(AF_INET, SOCK_STREAM, 0);

    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    bind(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr));

    listen(sockfd, 5);

    int addr_len = sizeof(client_addr);
    client_sock = accept(sockfd, (struct sockaddr*)&client_addr, &addr_len);

    recv(client_sock, buffer, sizeof(buffer), 0);

    printf("%s
", buffer);

    send(client_sock, "Hello, client!", strlen("Hello, client!"), 0);

    close(client_sock);
    close(sockfd);

    return 0;
}

2. UDP Protocol

UDP (User Datagram Protocol) is a connectionless, unreliable transmission protocol that does not guarantee data The reliability and sequence are suitable for some scenarios with high real-time requirements.

The following is a simple example of using UDP protocol for client-server communication:

// UDP client
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>

int main() {
    int sockfd;
    struct sockaddr_in server_addr;
    char buffer[1024];

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

    sendto(sockfd, "Hello, server!", strlen("Hello, server!"), 0, (struct sockaddr*)&server_addr, sizeof(server_addr));

    recv(sockfd, buffer, sizeof(buffer), 0);

    printf("%s
", buffer);

    close(sockfd);

    return 0;
}

// UDP server
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>

int main() {
    int sockfd;
    struct sockaddr_in server_addr, client_addr;
    char buffer[1024];

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    bind(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr));

    int addr_len = sizeof(client_addr);
    recvfrom(sockfd, buffer, sizeof(buffer), 0, (struct sockaddr*)&client_addr, &addr_len);

    printf("%s
", buffer);

    sendto(sockfd, "Hello, client!", strlen("Hello, client!"), 0, (struct sockaddr*)&client_addr, addr_len);

    close(sockfd);

    return 0;
}

除了TCP和UDP协议外，Linux协议栈还支持诸如IP协议、ICMP协议、ARP协议等网络协议，它们共同构成了一个完整的网络通信体系，为应用程序提供了丰富的网络通信功能。通过学习和理解这些网络协议，我们可以更好地利用Linux操作系统进行网络编程，构建高效可靠的网络应用。

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