Linux网络编程8——对TCP与UDP的简易封装

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:[email protected] 

    > 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。