linux 套接字编程入门--Hello World

时间：2023-03-08 15:48:16

　　下述代码是linux套接字编程的入门代码.分为服务端和客户端源码.

　　服务端代码的主要流程是绑定ip地址和端口号建立套接字,等待客户端发起访问.接受客户端请求之后,向客户端发送字符串"hello world",关闭套接字,结束程序.

　　客户端代码的主要流程是向服务端对应的套接字发起请求,读取服务端发送的数据,并且打印出来.

　　代码已经详细注释,更多细节不再赘述.

server.cpp

#include<stdio.h>

#include<stdlib.h>

#include<unistd.h>

#include<arpa/inet.h>

#include<sys/socket.h>

#include<netinet/in.h>

#include <string.h>

int main(){

    //创建套接字

    /*

     * AF_INET is an address family that is used to designate

     * the type of addresses that your socket can communicate

     * with (in this case, Internet Protocol v4 addresses).

     * When you create a socket, you have to specify its address family,

     * and then you can only use addresses of that type with the socket.

     * The Linux kernel, for example, supports 29 other address families

     * such as UNIX (AF_UNIX) sockets and IPX (AF_IPX), and also communications with IRDA

     * and Bluetooth 
     * (AF_IRDA and AF_BLUETOOTH, but it is doubtful you'll use these at such a low level).

     * For the most part, sticking with AF_INET for socket programming over

     * a network is the safest option.

     * There is also AF_INET6 for Internet Protocol v6 addresses

     */

    /*

     * SOCK_STREAM

     * Provides sequenced, reliable, two-way, connection-

     * based byte streams.  An out-of-band data transmission

     * mechanism may be supported.

     */

    //IPPROTO_TCP 采用TCP协议

    int serv_sock =socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);

    //将套接字和IP 端口号进行绑定

    struct sockaddr_in serv_addr;

    //初始化结构体serv_addr

    memset(&serv_addr,,sizeof(serv_addr));

    //使用ipv4地址

    serv_addr.sin_family=AF_INET;

    //设置ip地址

    serv_addr.sin_addr.s_addr=inet_addr("127.0.0.1");

    //设置端口号

    serv_addr.sin_port =htons();

    //将套接字和结构体进行绑定 结构体中存储了套接字的协议 端口号  以及ip地址

    bind(serv_sock,(struct sockaddr*)&serv_addr,sizeof(serv_addr));

    //进入监听状态,等待用户发起请求

    //进入被动监听状态,套接字一直处于睡眠状态,直至客户端发起请求才会被重新唤醒

    listen(serv_sock,);

    //客户端请求对应的套接字结构体

    struct sockaddr_in client_addr;

    //客户端请求套接字结构体的大小

    socklen_t  client_addr_size =sizeof(client_addr);

    //用于接受客户端的请求

    int client_sock =accept(serv_sock,(struct sockaddr *)&client_addr,&client_addr_size);

    char str[]="hello world";

    //向客户端发送数据

    //向客户端套接字中写入数据

    write(client_sock,str,sizeof(str));

    //关闭套接字

    close(client_sock);

    close(serv_sock);

    return ;

}

client.cpp

#include<stdio.h>

#include<cstring>

#include<stdlib.h>

#include<unistd.h>

#include <arpa/inet.h>

#include<sys/socket.h>

int main(){

    /*

     * This constant has the value 0.
     * It's actually an automatic choice depending on socket type and family.

     * If you use it, and if the socket type is SOCK_STREAM and the family is AF_INET,

     * then the protocol will automatically be TCP (exactly the same as if you'd used IPPROTO_TCP).

     * Buf if you use IPPROTO_IP together with AF_INET and SOCK_RAW, you will have an error,

     * because the kernel cannot choose a protocol automatically in this case.

     */

    int sock =socket(AF_INET,SOCK_STREAM,IPPROTO_IP);

    struct sockaddr_in serv_addr;

    memset(&serv_addr,,sizeof(serv_addr));

    serv_addr.sin_family=AF_INET;

    serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

    serv_addr.sin_port= htons();

    //通过connect函数向客户端发起请求,服务器的套接字信息存储在结构体serv_addr中

    connect(sock,(struct sockaddr*)&serv_addr,sizeof(serv_addr));

    char buffer[];

    //通过read从套接字中读取数据

    read(sock,buffer,sizeof(buffer)-);

    printf("message from server: %s\n",buffer);

    //关闭套接字

    close(sock);

    return ;

}

参考:

  1. stack_overflow
  2. man7
  3. c语言中文网

　　

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