引言
每次使用socket通信，都会有很对相似的操作。本文，会对TCP与UDP通信做一简单封装，并生成动态库。
代码
my_socket.h
#ifndef __MY_SOCKET_H__
#define __MY_SOCKET_H__
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define IN
#define OUT
#define IN_OUT
#define MY_TCP 1
#define MY_UDP 2
typedef struct sockaddr* pSA ;
typedef struct sockaddr_in SA ;
#define MY_ASSERT(flag,msg) ( (flag) ? NULL : ( fprintf(stdout,msg), exit(EXIT_FAILURE) ) ) // NULL代表什么也不做
void my_socket(OUT int *local_sfd, int protocal, char *local_ip, int local_port);
void my_listen(int local_sfd, int backlog);
void my_accept(OUT int *peer_sfd, int local_sfd, OUT pSA peer_addr, IN_OUT int *addr_len );
void my_connect(int local_sfd, pSA peer_addr, int addr_len);
void my_recv(OUT int *recv_len, int peer_sfd, IN_OUT void *base, int len);
void my_send(OUT int *send_len, int peer_sfd, void *base, int len);
void my_recvfrom(OUT int *recvfrom_len, int peer_sfd, IN_OUT void *base, int len, OUT pSA peer_addr, IN_OUT int *addr_len);
void my_sendto(OUT int *sendto_len, int peer_sfd, OUT void *base, int len, pSA peer_addr, int addr_len);
void my_close(int sfd);
#endif
my_socket.c
/*************************************************************************
> File Name: my_socket.c
> Author: KrisChou
> Mail:zhoujx0219@163.com
> Created Time: Mon 01 Sep 2014 06:54:48 PM CST
************************************************************************/
/* 本代码用于在一台主机上模拟socket通信。因此IP地址对于server和client而言是一样的。
* 为了简化代码，此处即使是客户端，也提前分配好端口号。事实上，主动方的端口号可以由系统分配，不用提前绑定
* --> 无论server或者client，都会预先绑定本地socket */
/* 本代码local_sfd代表本地socket描述符。
* 对于服务器而言，就是用于监听的socket; 对于客户端而言就是用于通信的socket
* peer_sfd，代表与对方通信的socket描述符。
* 对于服务器而言，由accept以传出参数形式返回；对于客户端而言，就是本地socket */
#include "my_socket.h"
void my_socket(OUT int *local_sfd, int protocal, char *local_ip, int local_port)
{
MY_ASSERT(protocal == MY_TCP || protocal == MY_UDP, "wrong arg! protocal is MY_TCP or MY_UDP! \n");
/* 创建本地socket */
if(protocal == MY_TCP)
{
MY_ASSERT(-1 != (*local_sfd = socket(AF_INET, SOCK_STREAM, 0)), "tcp_socket init falure!\n");
}else if(protocal == MY_UDP)
{
MY_ASSERT(-1 != (*local_sfd = socket(AF_INET, SOCK_DGRAM, 0)), "udp_socket init failure!\n");
}
/* 将本地联系方式bind到本地socket */
SA local_addr;
memset(&local_addr, 0, sizeof(SA));
local_addr.sin_family = AF_INET;
local_addr.sin_port = htons(local_port);
local_addr.sin_addr.s_addr = inet_addr(local_ip);
MY_ASSERT( 0 == bind(*local_sfd, (pSA)&local_addr, sizeof(SA)), "bind failure!\n");
}
/*----------------------------- 以下针对TCP ----------------------------------------------------- */
/* server: listen + accept */
void my_listen(int local_sfd, int backlog)
{
MY_ASSERT( 0 == listen(local_sfd, backlog), "listen failure!\n");
}
void my_accept(OUT int *peer_sfd, int local_sfd, OUT pSA peer_addr, IN_OUT int *addr_len )
{
MY_ASSERT(-1 != (*peer_sfd = accept(local_sfd, peer_addr, addr_len)), "accept failure!\n");
}
/* client: connect */
void my_connect(int local_sfd, pSA peer_addr, int addr_len)
{
int cnt = 0;
// 10次连不上就退出程序
while(-1 == connect(local_sfd, peer_addr, addr_len))
{
cnt++;
if(cnt == 10)
{
printf("connect failure!\n");
exit(EXIT_FAILURE);
}
sleep(1);
}
}
/* recv and send */
void my_recv(OUT int *recv_len, int peer_sfd, IN_OUT void *base, int len)
{
MY_ASSERT(-1 != (*recv_len = recv(peer_sfd, base, len, 0)), "recv error! \n");
}
void my_send(OUT int *send_len, int peer_sfd, void *base, int len)
{
MY_ASSERT(-1 != (*send_len = send(peer_sfd, base, len, 0)), "send error! \n");
}
/*---------------------------- 以下针对UDP--------------------------------------------------------*/
void my_recvfrom(OUT int *recvfrom_len, int peer_sfd, IN_OUT void *base, int len, OUT pSA peer_addr, IN_OUT int *addr_len)
{
MY_ASSERT(-1 != (*recvfrom_len = recvfrom(peer_sfd, base, len, 0, peer_addr, addr_len)), "recvfrom failure!\n");
}
void my_sendto(OUT int *sendto_len, int peer_sfd, OUT void *base, int len, pSA peer_addr, int addr_len)
{
MY_ASSERT(-1 != (*sendto_len = sendto(peer_sfd, base, len, 0, peer_addr, addr_len)), "sendto failure!\n");
}
/* close */
void my_close(int sfd)
{
MY_ASSERT(0 == close(sfd), "close failure!\n");
}
生成动态库
gcc -fPIC -o my_socket.o -c my_socket.c //我的.h文件和.c文件在一个目录下，如果不在，请指定头文件位置
gcc -shared -o libmy_socket.so.1.0 my_socket.o
cp./libmy_socket.s0.1.0 /lib
cd /lib
ln -s libmy_socket.so.1.0 libmy_socket.so
我个人将头文件放在主目录的include文件夹下，方便以后查找和使用。(/home/purple/include)
测试代码
server.c
#include "my_socket.h"
#define IP "192.168.153.128"
#define PORT 8888
int main(int argc, char *argv[])
{
int fd_server, fd_client;
int val; //用4个字节的地址空间来传数据
int len;
my_socket(&fd_server, MY_TCP, IP, PORT);
my_listen(fd_server,5);
my_accept(&fd_client, fd_server, NULL, NULL);
printf("accept success!\n");
while(1)
{
my_recv(&len, fd_client, (void*)&val, sizeof(val));
printf("recv data: %d\n", val);
my_send(&len, fd_client, (void*)&val, sizeof(val));
printf("%d has sent!\n\n", val);
}
my_close(fd_client);
my_close(fd_server);
return 0;
}
client.c
#include "my_socket.h"
#define IP "192.168.153.128"
#define MY_PORT 6666
#define SERVER_PORT 8888
int main(int argc, char *argv[])
{
/* socket */
int fd_client;
my_socket(&fd_client, MY_TCP, IP, MY_PORT);
/* connect */
SA server_addr;
memset(&server_addr,0,sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(SERVER_PORT);
server_addr.sin_addr.s_addr = inet_addr(IP);
my_connect(fd_client, (pSA)&server_addr, sizeof(SA));
printf("connect success!\n");
/* 发送一个数据，并从服务器端返回这个数据 */
int val_in,val_out,len;
while(scanf("%d", &val_in) == 1)
{
my_send(&len,fd_client,(void*)&val_in,sizeof(int));
my_recv(&len,fd_client,(void*)&val_out,sizeof(int));
printf("recv fron server: %d\n", val_out);
}
my_close(fd_client);
return 0;
}
编译如下
gcc -o server server.c -lmy_socket -I/home/purple/include
gcc -o client client.c -lmy_socket -I/home/purple/include
经测试没有问题。
注意
短路运算（||）必须有返回值，而exit返回值为void，因此头文件中的宏定义，我们没有使用短路运算，而是使用了三目运算符。
