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linux网络编程:使用多进程实现socket同时收发数据

2016-09-27 23:58 661 查看
    前面已讲过使用一个进程实现服务端和客户端P2P通信的实例，但是它只能同时处理一个客户端的连接。如果要实现并发处理多个客户端的连接并且实现P2P通信，可以使用多进程来处理。相比与多线程来说，多进程耗费的系统资源是比较多的，后续会介绍使用线程池实现简单的数据收发。

    使用多进程并发处理多个client请求以及实现P2P通信，父进程专门监听端口，每监听到一个连接就创建一个子进程处理这个客户端，于此同时，在子进程中创建一个孙子进程来处理数据的读取，在子进程实现数据的发送。如果客户端断开连接，recv函数会返回参数0，recv函数所在进程发送信号给send函数所在进程，然后退出recv进程，send函数所在进程接收到信号SIGUSR1就退出该进程。在多进程中，子进程退出时会产生僵尸进程，僵尸进程的处理有多种方法，最简单的就是直接忽视SIGCHLD信号。

下面直接上代码：

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

#define MAXLINE 256
#define PORT	6666

/*进程退出函数*/
void process_out(int signo)
{
exit(EXIT_SUCCESS);
}

/*socket write 函数*/
void write_func(int pid, int fd)
{
char* write = "I am server";

printf("write id = %d\n",pid);

signal(SIGUSR1,process_out);  /* 注册信号SIGUSR1，该信号由read 进程发送过来。*/
while(1)
{
sleep(1);
send(fd,write,strlen(write)+1,0);
}
}

/*socket read 函数*/
void read_func(int pid, int fd)
{
char readbuff[MAXLINE];
int n = 0;

printf("read id = %d \n",pid);

memset(&readbuff,0,sizeof(readbuff));

while(1)
{
n = recv(fd, readbuff, MAXLINE, 0);  /*recv 在这里是阻塞运行*/
if(n > 0) 			/*客户端有数据发送过来*/
{
printf("server recv data: %s \n",readbuff);
}
else if(n == 0)		/*客户端断开了连接*/
{
break;
}
};

kill(pid, SIGUSR1); /*发送信号SIGUSR1 到write进程*/
exit(EXIT_SUCCESS); /*进程退出*/
}

int main(void)
{
int listenfd,connetfd;
int on = 1;
int addrlen = 0;
pid_t pid, pid_child, pid_send;
struct sockaddr_in server_addr;
struct sockaddr_in client_addr;

if ((listenfd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
{
printf("create socket err \n");
}

/*设置服务端地址*/
addrlen = sizeof(struct sockaddr_in);
memset(&server_addr, 0, addrlen);
server_addr.sin_family = AF_INET;    /*AF_INET表示 IPv4 Intern 协议*/
server_addr.sin_addr.s_addr = htonl(INADDR_ANY); /*INADDR_ANY 可以监听任意IP */
server_addr.sin_port = htons(PORT);  /*设置端口*/

/*对套接字进行设置*/
if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
{
printf("bind socket error: %s(errno: %d)\n",strerror(errno),errno);
exit(0);
}

/*绑定地址结构到套接字描述符*/
if( bind(listenfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1)
{
printf("bind socket error: %s(errno: %d)\n",strerror(errno),errno);
exit(0);
}

/*设置监听队列，这里设置为10，表示可以同时处理10个客户端的连接*/
if( listen(listenfd, 10) == -1)
{
printf("listen socket error: %s(errno: %d)\n",strerror(errno),errno);
exit(0);
}

printf("wait client accpt \n");
while(1)
{
/*接收客户端的连接，这里会阻塞，直到有客户端连接*/
if( (connetfd = accept(listenfd, (struct sockaddr*)&client_addr, &addrlen)) == -1)
{
printf("accept socket error: %s(errno: %d)",strerror(errno),errno);
continue;
}

signal(SIGCHLD, SIG_IGN); /*忽略SIGCHLD，避免僵尸进程*/
pid = fork();
if(pid == -1)
{
printf("fork err \n");
}

if(pid == 0)					/* 子进程*/
{
pid_child = fork();
if(pid_child == 0)  		/*孙子进程*/
{
pid_send = getpid(); 	/*获取孙子进程ID*/
read_func(pid_send, connetfd);
}
else
{
pid_send = getpid(); 	/* 获取子进程ID*/
write_func(pid_send,connetfd);
}
}

}
}



    测试程序这里不再实现，将上面代码在PC机上编译运行，在手机端使用网络助手工具直接连接PC机的6666端口，可以看到如下运行结果：

root@ubuntu:/home/share/Socket/process# ./process_server
wait client accpt
write id = 3883
read id = 3884
server recv data: I am client 1
server recv data: I am client 1
server recv data: I am client 1
server recv data: I am client 1
write id = 3885
read id = 3886
server recv data: I am client 1
server recv data: I am client 2
server recv data: I am client 1
server recv data: I am client 2
server recv data: I am client 1
write id = 3887
read id = 3888
server recv data: I am client 2
server recv data: I am client 1
server recv data: I am client 2
server recv data: I am client 1
server recv data: I am client 2
server recv data: I am client 1
server recv data: I am client 1
server recv data: I am client 1
^C
root@ubuntu:/home/share/Socket/process#
    先连接三个客户端，然后再断开连接，客户端收到的数据不再贴出。于此同时我们使用PS查看进程状态：

root@ubuntu:/home/share# ps aux |grep process_server
root       3882  0.0  0.0   4164   348 pts/0    S+   22:38   0:00 ./process_server
root       3883  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3884  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3885  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3886  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3887  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3888  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3890  0.0  0.0  13588   940 pts/2    S+   22:38   0:00 grep --color=auto process_server
root@ubuntu:/home/share# ps aux |grep process_server
root       3882  0.0  0.0   4164   348 pts/0    S+   22:38   0:00 ./process_server
root       3883  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3884  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3885  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3886  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3894  0.0  0.0  13588   940 pts/2    S+   22:38   0:00 grep --color=auto process_server
root@ubuntu:/home/share# ps aux |grep process_server
root       3882  0.0  0.0   4164   348 pts/0    S+   22:38   0:00 ./process_server
root       3883  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3884  0.0  0.0   4164    88 pts/0    S+   22:38   0:00 ./process_server
root       3896  0.0  0.0  13588   940 pts/2    S+   22:39   0:00 grep --color=auto process_server
root@ubuntu:/home/share# ps aux |grep process_server
root       3882  0.0  0.0   4164   348 pts/0    S+   22:38   0:00 ./process_server
root       3898  0.0  0.0  13588   944 pts/2    S+   22:39   0:00 grep --color=auto process_server
root@ubuntu:/home/share#
    可以看到并未产生僵尸进程，但是如果把上面程序的signal(SIGCHLD, SIG_IGN);去掉，我们就可以看到产生了僵尸进程。

root@ubuntu:/home/ysj000# ps aux |grep process_server
root       3812  0.0  0.0   4164   352 pts/0    S+   22:24   0:00 ./process_server
root       3814  0.0  0.0   4164    92 pts/0    S+   22:25   0:00 ./process_server
root       3815  0.0  0.0   4164    92 pts/0    S+   22:25   0:00 ./process_server
root       3816  0.0  0.0   4164    92 pts/0    S+   22:25   0:00 ./process_server
root       3817  0.0  0.0   4164    92 pts/0    S+   22:25   0:00 ./process_server
root       3819  0.0  0.0  13588   944 pts/2    S+   22:25   0:00 grep --color=auto process_server
root@ubuntu:/home/ysj000# ps aux |grep process_server
root       3812  0.0  0.0   4164   352 pts/0    S+   22:24   0:00 ./process_server
root       3814  0.0  0.0   4164    92 pts/0    S+   22:25   0:00 ./process_server
root       3815  0.0  0.0   4164    92 pts/0    S+   22:25   0:00 ./process_server
root       3816  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3821  0.0  0.0  13588   944 pts/2    S+   22:25   0:00 grep --color=auto process_server
root@ubuntu:/home/ysj000# ps aux |grep process_server
root       3812  0.0  0.0   4164   352 pts/0    S+   22:24   0:00 ./process_server
root       3814  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3816  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3823  0.0  0.0  13588   944 pts/2    S+   22:26   0:00 grep --color=auto process_server
root@ubuntu:/home/ysj000# ps aux |grep process_server
root       3812  0.0  0.0   4164   352 pts/0    S+   22:24   0:00 ./process_server
root       3814  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3816  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3824  0.0  0.0   4164    92 pts/0    S+   22:26   0:00 ./process_server
root       3825  0.0  0.0   4164    92 pts/0    S+   22:26   0:00 ./process_server
root       3827  0.0  0.0  13588   944 pts/2    S+   22:26   0:00 grep --color=auto process_server
root@ubuntu:/home/ysj000# ps aux |grep process_server
root       3812  0.0  0.0   4164   352 pts/0    S+   22:24   0:00 ./process_server
root       3814  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3816  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3824  0.0  0.0   4164    92 pts/0    S+   22:26   0:00 ./process_server
root       3825  0.0  0.0   4164    92 pts/0    S+   22:26   0:00 ./process_server
root       3830  0.0  0.0   4164    92 pts/0    S+   22:27   0:00 ./process_server
root       3831  0.0  0.0   4164    92 pts/0    S+   22:27   0:00 ./process_server
root       3833  0.0  0.0  13588   940 pts/2    S+   22:27   0:00 grep --color=auto process_server
root@ubuntu:/home/ysj000# ps aux |grep process_server
root       3812  0.0  0.0   4164   352 pts/0    S+   22:24   0:00 ./process_server
root       3814  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3816  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3824  0.0  0.0   4164    92 pts/0    S+   22:26   0:00 ./process_server
root       3825  0.0  0.0   4164    92 pts/0    S+   22:26   0:00 ./process_server
root       3830  0.0  0.0      0     0 pts/0    Z+   22:27   0:00 [process_server] <defunct>
root       3835  0.0  0.0  13588   944 pts/2    S+   22:27   0:00 grep --color=auto process_server
root@ubuntu:/home/ysj000# ps aux |grep process_server
root       3812  0.0  0.0   4164   352 pts/0    S+   22:24   0:00 ./process_server
root       3814  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3816  0.0  0.0      0     0 pts/0    Z+   22:25   0:00 [process_server] <defunct>
root       3824  0.0  0.0      0     0 pts/0    Z+   22:26   0:00 [process_server] <defunct>
root       3830  0.0  0.0      0     0 pts/0    Z+   22:27   0:00 [process_server] <defunct>
root       3839  0.0  0.0  13588   944 pts/2    S+   22:27   0:00 grep --color=auto process_server

注意1：在上面的代码中，我们直接忽视了SIGCHLD 信号来避免产生僵尸进程，在linux系统中是可以的，但是在其他的一些系统不一定都可以。另外，直接忽视SIGCHLD信号会造成一些其他的影响：会影响system函数的正常使用。system里面会将sigchld设置为阻塞，因为system里面会调用fork，然后执行命令，最后通过waitpid等待子进程的返回，不将sigchld设置为阻塞有可能信号被别人处理掉，system无法获得到信号就会报错，错误号echld，no child processes，这就是因为信号被别人处理了，其实命令是运行成功的。而忽略sigchld信号就会导致这一问题。所以正常使用的时候需要多加注意（可以使用wait
或waitpid 来避免僵尸进程）如下：

void sig_chld(int signo)
{
pid_t	pid;
int 	stat;
while ((pid = waitpid(-1,stat,WNOHANG))>0)
{
//printf("child %d terminated \n",pid);
}
return ;
}


信号注册 signal(SIGCHLD, sig_chld);  

注意2：如果我们不主动收发数据也想检测到TCP连接的对方已经退出或是崩溃，我们可以使用套接字选项SO_KEEPALIVE来实现。
                                            

                                        

                        
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                         标签： 
                                                linux
                                                socket
                                                多线程
                                                p2p
                                                网络编程
                                                

                        

                    


                

            


            

                
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