[系统运维]我的物联网之路—Linux中的C编程—网络编程

套接字

Linux中的网络编程通过socket接口实现。Socket既是一种特殊的IO也是一种文件描述符。套接字有三种：流式套接字(TCP)、数据报套接字(UDP)、原始套接字

字节序列转换

因为每一个机器内部对变量的字节存储顺序不同，而网络传输的数据大家是一定要统一顺序的。

服务端和客户端使用TCP协议流程图

服务端和客户端使用UDP协议流程图

Example

基础编程

client

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

#define SERVER_PORT 1234
int main(int argc, char *argv[])
{
    char rBuf[20];
    // int ret, fd[2], wCnt_f, wCnt_s;
    int socketFd;
    struct sockaddr_in s_serverAddr;
    socketFd = socket(AF_INET, SOCK_STREAM, 0);
    if (socketFd < 0)
    {
        perror("socket:");
        exit(-1);
    }

    printf("socket success! \n");

    s_serverAddr.sin_family = AF_INET;

    s_serverAddr.sin_port = htons(SERVER_PORT);

    s_serverAddr.sin_addr.s_addr = inet_addr(argv[1]);

    if (connect(socketFd, (struct sockaddr *)&s_serverAddr, sizeof(s_serverAddr)) < 0)
    {
        perror("connect:");
        exit(0);
    }
    printf("connect success!\n");
    int senlen = send(socketFd, "hello world", sizeof("hello world") + 1, 0);
    if (senlen < 0)
    {
        perror("send:");
        exit(0);
    }
    printf("(s)send success!\n");
    close(socketFd);
    return 0;
}

server

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

#define SERVER_PORT 1234
int main(int argc, char *argv[])
{
    char buf[20];
    int socketFd, clientAddrLen, clientsocketFd;
    struct sockaddr_in s_serverAddr;
    struct sockaddr_in s_clientAddr;
    socketFd = socket(AF_INET, SOCK_STREAM, 0);
    if (socketFd < 0)
    {
        perror("socket:");
        exit(-1);
    }
    printf("socket success!\n");
    s_serverAddr.sin_family = AF_INET;
    s_serverAddr.sin_port = htons(SERVER_PORT);
    s_serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    if (bind(socketFd, (struct sockaddr *)&s_serverAddr, sizeof(s_serverAddr)) < 0)
    {
        perror("bind:");
        exit(0);
    }
    printf("bind success!\n");
    if (listen(socketFd, 10) < 0)
    {
        perror("listen:");
        exit(0);
    }
    printf("listen success!\n");
    clientsocketFd = accept(socketFd, (struct sockaddr *)&s_clientAddr, &clientAddrLen);
    if (clientsocketFd < 0)
    {
        perror("accept:");
        exit(0);
    }
    printf("accept success!\n");
    int recvlen = recv(clientsocketFd, buf, 20, 0);
    if (recvlen < 0)
    {
        perror("recv:");
        exit(0);
    }
    printf("recv success!\n");
    printf("recv(%d):%s \n", recvlen, buf);
    close(socketFd);
    close(clientsocketFd);
}

函数参考

套接字地址结构

字节序列转换