linux 套接字编程入门--Hello World

　　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,0,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(2896);
//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,20);
//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 0;
}

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,0,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(2896);
//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[40];
//通过read从套接字中读取数据
read(sock,buffer,sizeof(buffer)-1);

printf("message from server: %s\n",buffer);
//关闭套接字
close(sock);
return 0;

}

参考:

stack_overflow

man7

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