linux 網絡編程:使用兩線程實現socket同時收發數據

http://blog.csdn.net/li_wen01/article/details/52665505

工作中最近有使用到socket 向客戶端同時發送和接收數據，因為是嵌入式linux設備，且要求只能同時一個客戶端連接該端口。考慮到節省系統資源，只創建了兩個線程分別實現服務端的收發數據。下面直接上代碼，該代碼為在PC機上程序，已作詳細注釋。

server.c

[objc]?view plaincopy  
 print?
 #include<stdio.h>??
 #include<stdlib.h>??
 #include<string.h>??
 #include<errno.h>??
 #include<sys/types.h>??
 #include<sys/socket.h>??
 #include<netinet/in.h>??
 #include<termios.h>??
 #include<sys/types.h>?????
 #include<sys/stat.h>??????
 #include<fcntl.h>??
 #include<unistd.h>??
 #include<sys/ioctl.h>??
 #include<signal.h>??
 ??
 #define?MAXLINE?256??
 #define?PORT????6666??
 int?listenfd;??
 int?connfd;??
 pthread_t?read_id,?write_id;??
 ??
 /*?
 linux?ctrl?+?C?會產生?SIGINT信號?
 接收到SIGINT?信號進入該函數?
 */??
 void?stop(int?signo)??
 {??
 ????printf("stop\n");??
 ????close(connfd);????
 ????close(listenfd);??
 ?????_exit(0);??
 }??
 ??
 /*?
 當客戶端斷開連接的時候，?
 在服務端socket?send進程可以收到收到信號SIGPIPE，?
 收到SIGPIPE信號進入該函數結束創建的線程。?
 */??
 void?signal_pipe(int?signo)??
 {??
 ????pthread_kill(read_id,SIGQUIT);//向read線程發送SIGQUIT??
 ????pthread_join(read_id,NULL);???//阻塞線程運行，直到read?線程退出。??
 ??????
 ????close(connfd);????????????????//關閉連接??
 ????printf("read?pthread?out?\n");??
 ??????
 ????pthread_exit(0);??????????????//結束write?線程??
 }??
 ??
 /*?
 read?線程接收到SIGQUIT信號，?
 執行線程退出操作?
 */??
 void?pthread_out(int?signo)??
 {??
 ????pthread_exit(0);??
 }??
 ??
 /*?
 read?線程執行函數?
 */??
 void*?read_func(void*?arg)??
 {??
 ????char?readbuff[MAXLINE];??
 ????int?n?=?0;??
 ????int?fd;??
 ??
 ????fd?=?*(int*)arg;????/*main?主進程傳遞過來的連接文件描述符*/??
 ????memset(&readbuff,0,sizeof(readbuff));??
 ??
 ????signal(SIGQUIT,pthread_out);?/*?注冊SIGQUIT?信號*/???
 ????while(1)??
 ????{??
 ????????n?=?recv(fd,?readbuff,?MAXLINE,?0);??/*recv?在這里是阻塞運行*/??
 ????????if(n?>?0)??
 ????????{??
 ????????????printf("server?recv?data:?%s?\n",readbuff);??
 ????????}??
 ????};??
 }??
 /*?
 write?線程執行函數?
 */??
 void*?write_func(void*?arg)??
 {??
 ????char?writebuff[MAXLINE];??
 ????char*?write?=?"I?am?server";??
 ????unsigned?char?i?=?0;??
 ????int?num?=?0;??
 ????int?fd;??
 ??
 ????fd?=?*(int*)arg;??
 ????memset(&writebuff,0,sizeof(writebuff));??
 ??????
 ????signal(SIGPIPE,signal_pipe);?/*?注冊?SIGPIPE信號?*/??
 ????while(1)??
 ????{??
 ????????sleep(1);??
 ????????send(fd,write,strlen(write)+1,0);/*向客戶端發送數據*/??
 ????}??
 }??
 ??
 int?main(int?argc,?char**?argv)??
 {??
 ????char?buff[MAXLINE];??
 ????int?num;??
 ????int?addrlen;??
 ????struct?sockaddr_in?server_addr;??/*服務器地址結構*/??
 ????struct?sockaddr_in?client_addr;??/*客戶端地址結構*/??
 ??
 ????if((listenfd?=?socket(AF_INET,SOCK_STREAM,0))?==?-1)/*建立一個流式套接字*/??
 ????{??
 ????????printf("create?socket?error:?%s(errno:?%d)\n",strerror(errno),errno);??
 ????????exit(0);??
 ????}??
 ??????
 ????/*設置服務端地址*/??
 ????addrlen?=?sizeof(struct?sockaddr_in);??
 ????memset(&server_addr,?0,?addrlen);??
 ????server_addr.sin_family?=?AF_INET;????/*AF_INET表示?IPv4?Intern?協議*/??
 ????server_addr.sin_addr.s_addr?=?htonl(INADDR_ANY);?/*INADDR_ANY?可以監聽任意IP?*/??
 ????server_addr.sin_port?=?htons(PORT);?/*設置端口*/??
 ??????
 ????/*綁定地址結構到套接字描述符*/??
 ????if(?bind(listenfd,?(struct?sockaddr*)&server_addr,?sizeof(server_addr))?==?-1)??
 ????{??
 ????????printf("bind?socket?error:?%s(errno:?%d)\n",strerror(errno),errno);??
 ????????exit(0);??
 ????}??
 ??
 ????/*設置監聽隊列，這里設置為1，表示只能同時處理一個客戶端的連接*/??
 ????if(?listen(listenfd,?1)?==?-1)??
 ????{??
 ????????printf("listen?socket?error:?%s(errno:?%d)\n",strerror(errno),errno);??
 ????????exit(0);??
 ????}??
 ??????
 ????signal(SIGINT,stop);?/*注冊SIGINT?信號*/??
 ????while(1)??
 ????{?????
 ????????printf("wait?client?accpt?\n");??
 ????????if(?(connfd?=?accept(listenfd,?(struct?sockaddr*)&client_addr,?&addrlen))?==?-1)/*接收客戶端的連接，這里會阻塞，直到有客戶端連接*/??
 ????????{??
 ????????????printf("accept?socket?error:?%s(errno:?%d)",strerror(errno),errno);??
 ????????????continue;??
 ????????}??
 ??????
 ????????if(pthread_create(&read_id,NULL,read_func,&connfd))/*創建?read?線程*/??
 ????????{??
 ????????????printf("pthread_create?read_func?err\n");??
 ????????}??
 ??
 ????????if(pthread_create(&write_id,NULL,write_func,&connfd))/*創建?write?線程*/??
 ????????{??
 ????????????printf("pthread_create?write_func?err\n");??
 ????????}??
 ??????????
 ????????pthread_join(write_id,NULL);?/*阻塞，直到write進程退出后才進行新的客戶端連接*/??
 ????????printf("write?pthread?out?\n");??
 ????}??
 }??

? ? 這里需要特別注意線程資源的回收，因為每次與客戶端建立連接，服務端都會創建連個線程，因此我們需要在客戶端斷開連接時回收線程資源。在這里有兩種方式來檢測客戶端是否已經斷開連接。第一：上面server.c服務端使用的，當客戶端斷開連接時，send 所在的進程會收到一個SIGPIPE信號，服務端收到SIGPIPE信號就進行線程退出操作。第二：recv函數在對方斷開連接它會返回參數0，根據該參數也可以知道客戶端已經斷開了連接。在下面你的client.c客戶端測試程序使用的就是這種方式。

? ? 這里還有一個問題，signal(SIGPIPE,signal_pipe)函數的注冊，我本來是把它放置在主線程main函數中，然后在signal_pipe 同時回收read 和 write線程，結果read進程可以正常回收，write線程卻回收失敗，具體原因也不清楚，求高人指點。于是我就是用SIGQUIT信號，在write線程收到SIGPIPE信號時，通知read線程退出，直到其退出再退出write線程。這樣就實現了系統資源的回收。

client客戶端測試程序：

[objc]?view plaincopy  
 print?
 #include<stdio.h>?????????
 #include<stdlib.h>??
 #include<string.h>??
 #include<errno.h>??
 #include<sys/types.h>??
 #include<sys/socket.h>??
 #include<netinet/in.h>??
 #include<termios.h>??
 #include<sys/types.h>?????
 #include<sys/stat.h>??????
 #include<fcntl.h>??
 #include<unistd.h>??
 #include<sys/ioctl.h>??
 #include<signal.h>??
 ??
 #define?MAXLINE?256??
 #define?PORT????6666??
 int?fd;??
 /*?
 linux?ctrl?+?C?會產生?SIGINT信號?
 接收到SIGINT?信號進入該函數?
 */??
 void?stop(int?signo)??
 {??
 ????printf("client?stop\n");??
 ????close(fd);????
 ????_exit(0);??
 }??
 ??
 /*客戶端處理函數*/??
 void?client_process(void)??
 {??
 ????char?readbuff[MAXLINE];??
 ????char?writebuff[MAXLINE];??
 ????charchar?*?write?=?"I?am?client";??
 ????int?num?=?0;??
 ??????
 ????while(1)??
 ????{??
 ????????num?=?recv(fd,readbuff,MAXLINE,0);/*接收服務端的數據，recv在這里如果沒有數據會阻塞*/??
 ????????if(num?>?0)??
 ????????{??
 ????????????printf("client?read?data?:?%s?\n",readbuff);??
 ????????????send(fd,?write,?strlen(write)+1,?0);?/*接收到數據后再向服務端發送一個字符串*/??
 ????????}??
 ????????else?if(num?==?0)/*recv返回值為0?的時候表示服務端已經斷開了連接*/??
 ????????{??
 ????????????stop(1);?/*執行退出操作*/??
 ????????}??
 ????}??
 }??
 ??
 int?main(int?argc,?char**?argv)??
 {??
 ????struct?sockaddr_in?server_addr;??
 ????struct?sockaddr_in?client_addr;??
 ????int?ret;??
 ??
 ????fd?=?socket(AF_INET,SOCK_STREAM,0);/*建立流式套接字*/??
 ????if(fd?<?0)??
 ????{??
 ????????printf("clinet?socket?err?\n");??
 ????}??
 ??
 ????/*設置服務端地址*/??
 ????memset(&server_addr,0,sizeof(server_addr));??
 ????server_addr.sin_family?=?AF_INET;???????????????/*AF_INET表示?IPv4?Intern?協議*/??
 ????server_addr.sin_addr.s_addr?=?htonl(INADDR_ANY);/*INADDR_ANY?可以監聽任意IP?*/??
 ????server_addr.sin_port?=?htons(PORT);?????????????/*設置端口*/??
 ??
 ????inet_pton(AF_INET,argv[1],&server_addr.sin_addr);/*將用戶輸入的字符串類型的IP地址轉為整型*/??
 ????connect(fd,(struct?sockaddr*)&server_addr,sizeof(server_addr));/*連接服務器*/??
 ??????
 ????signal(SIGINT,stop);????/*注冊SIGINT信號*/??
 ????client_process();???????/*進入處理函數*/??
 ??????
 ????close(fd);/*關閉文件*/??
 ????return?0;??
 }??

? ? 在客戶端是用recv 函數的返回值判斷服務端是否斷開連接而不是SIGPIPE信號，主要是在這程序中，我的實現是send函數在接收到服務端的數據才發送，所以如果在這里不會觸發SIGPIPE信號。如果要實現客戶端的獨立收發，可以模仿服務端的實現方式，這里不再現實。

下面是測試執行情況：

[objc]?view plaincopy  
 print?
 root@ubuntu:/home/share/Socket#?./server???
 wait?client?accpt???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 read?pthread?out???
 write?pthread?out???
 wait?client?accpt???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 read?pthread?out???
 write?pthread?out???
 wait?client?accpt??
 ??
 ??
 ??
 root@ubuntu:/home/share/Socket#?./client?127.0.0.1??
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 ^Cclient?stop??
 root@ubuntu:/home/share/Socket#?./client?127.0.0.1??
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 ^Cclient?stop??
 root@ubuntu:/home/share/Socket#???

? ? 執行服務端從程序等待客戶連接，執行客戶端程序與服務端建立連接，服務端每秒向客戶端發送字符串：I am server，客戶端接收到數據后向服務端發送字符串： I am client 。在client端按下ctrl + c 結束客戶端程序，服務端檢測到客戶端斷開連接后，關閉文件描述符，回收創建的read 和write 線程。

[objc]?view plaincopy  
 print?
 root@ubuntu:/home/share/Socket#?./server???
 wait?client?accpt???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 server?recv?data:?I?am?client???
 ^Cstop??
 root@ubuntu:/home/share/Socket#???
 ??
 root@ubuntu:/home/share/Socket#?./client?127.0.0.1??
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?read?data?:?I?am?server???
 client?stop??
 root@ubuntu:/home/share/Socket#??