如何知道客户端是否在套接字中终止
假设我写了这个代码后有一个连接的socket
if ((sd = accept(socket_d,(struct sockaddr *)&client_addr,&alen)) < 0) { perror("accept failedn"); exit(1); } 我如何知道客户端已退出的服务器端. 我的整个程序实际上做了以下.. >接受来自客户端的连接 如果你想看到整个代码…在这整个代码.我也遇到一个问题,每当我用Ctrl C杀死一个客户端,我的服务器突然终止..如果有人可以建议什么问题,这将是很好的 #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <signal.h> #include <errno.h> #include <pthread.h> /*CONSTANTS*/ #define DEFAULT_PORT 10000 #define LISTEN_QUEUE_LIMIT 6 #define TOTAL_CLIENTS 10 #define CHAR_BUFFER 256 /*GLOBAL VARIABLE*/ int current_client = 0; int connected_clients[TOTAL_CLIENTS]; extern int errno; void *client_handler(void * socket_d); int main(int argc,char *argv[]) { struct sockaddr_in server_addr;/* structure to hold server's address*/ int socket_d; /* listening socket descriptor */ int port; /* protocol port number */ int option_value; /* needed for setsockopt */ pthread_t tid[TOTAL_CLIENTS]; port = (argc > 1)?atoi(argv[1]):DEFAULT_PORT; /* Socket Server address structure */ memset((char *)&server_addr,sizeof(server_addr)); server_addr.sin_family = AF_INET; /* set family to Internet */ server_addr.sin_addr.s_addr = INADDR_ANY; /* set the local IP address */ server_addr.sin_port = htons((u_short)port); /* Set port */ /* Create socket */ if ( (socket_d = socket(PF_INET,SOCK_STREAM,0)) < 0) { fprintf(stderr,"socket creation failedn"); exit(1); } /* Make listening socket's port reusable */ if (setsockopt(socket_d,SOL_SOCKET,SO_REUSEADDR,(char *)&option_value,sizeof(option_value)) < 0) { fprintf(stderr,"setsockopt failuren"); exit(1); } /* Bind a local address to the socket */ if (bind(socket_d,(struct sockaddr *)&server_addr,sizeof(server_addr)) < 0) { fprintf(stderr,"bind failedn"); exit(1); } /* Specify size of request queue */ if (listen(socket_d,LISTEN_QUEUE_LIMIT) < 0) { fprintf(stderr,"listen failedn"); exit(1); } memset(connected_clients,sizeof(int)*TOTAL_CLIENTS); for (;;) { struct sockaddr_in client_addr; /* structure to hold client's address*/ int alen = sizeof(client_addr); /* length of address */ int sd; /* connected socket descriptor */ if ((sd = accept(socket_d,&alen)) < 0) { perror("accept failedn"); exit(1); } else printf("n I got a connection from (%s,%d)n",inet_ntoa(client_addr.sin_addr),ntohs(client_addr.sin_port)); if (pthread_create(&tid[current_client],NULL,(void *)client_handler,(void *)sd) != 0) { perror("pthread_create error"); continue; } connected_clients[current_client]=sd; current_client++; /*Incrementing Client number*/ } return 0; } void *client_handler(void *connected_socket) { int sd; sd = (int)connected_socket; for ( ; ; ) { ssize_t n; char buffer[CHAR_BUFFER]; for ( ; ; ) { if (n = read(sd,buffer,sizeof(char)*CHAR_BUFFER) == -1) { perror("Error reading from client"); pthread_exit(1); } int i=0; for (i=0;i<current_client;i++) { if (write(connected_clients[i],sizeof(char)*CHAR_BUFFER) == -1) perror("Error sending messages to a client while multicasting"); } } } } 我的客户端是(Maye在回答我的问题时无关紧要) #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <netdb.h> #include <string.h> #include <stdlib.h> void error(char *msg) { perror(msg); exit(0); } void *listen_for_message(void * fd) { int sockfd = (int)fd; int n; char buffer[256]; bzero(buffer,256); printf("YOUR MESSAGE: "); fflush(stdout); while (1) { n = read(sockfd,256); if (n < 0) error("ERROR reading from socket"); if (n == 0) pthread_exit(1); printf("nMESSAGE BROADCAST: %sYOUR MESSAGE: ",buffer); fflush(stdout); } } int main(int argc,char *argv[]) { int sockfd,portno,n; struct sockaddr_in serv_addr; struct hostent *server; pthread_t read_message; char buffer[256]; if (argc < 3) { fprintf(stderr,"usage %s hostname portn",argv[0]); exit(0); } portno = atoi(argv[2]); sockfd = socket(AF_INET,0); if (sockfd < 0) error("ERROR opening socket"); server = gethostbyname(argv[1]); if (server == NULL) { fprintf(stderr,"ERROR,no such hostn"); exit(0); } bzero((char *) &serv_addr,sizeof(serv_addr)); serv_addr.sin_family = AF_INET; bcopy((char *)server->h_addr,(char *)&serv_addr.sin_addr.s_addr,server->h_length); serv_addr.sin_port = htons(portno); if (connect(sockfd,&serv_addr,sizeof(serv_addr)) < 0) error("ERROR connecting"); bzero(buffer,256); if (pthread_create(&read_message,(void *)listen_for_message,(void *)sockfd) !=0 ) { perror("error creating thread"); } while (1) { fgets(buffer,255,stdin); n = write(sockfd,256); if (n < 0) error("ERROR writing to socket"); bzero(buffer,256); } return 0; } 解决方法
接受连接后,在特殊情况下,套接字上的recv()将返回0或-1.
摘自recv(3) man page:
所以,如果您的客户端正常退出,您将在某个时刻从recv()获取0.如果连接丢失了,你也可能得到-1,并检查相应的errno会告诉你连接是否丢失了一些其他错误.详见recv(3) man page. 编辑: 我看到你正在使用read().尽管如此,与recv()相同的规则也适用. 尝试向客户端写()时,您的服务器也可能会失败.如果您的客户端断开连接,write()将返回-1,并且可能将errno设置为EPIPE.此外,如果您不阻止/忽略此信号,SIGPIPE信号将发送给您进程并杀死他.而且您不会看到,这就是为什么当客户端按Ctrl-C时,您的服务器会终止. Ctrl-C终止客户端,因此关闭客户端套接字,使您的服务器的write()失败. 请参阅mark4o的答案,详细说明还有什么可能出错. (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |