嵌入式

linux c编程 TCP实例以及优化

2019-07-13 01:03发布

站内文章 / 嵌入式Linux
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文章代码来自于《嵌入式linux应用程序开发 标准教程》 第一个实例实现了服务器和客户端的TCP通信 第二个实例是在第一个的基础上使用了select函数实现多路复用 而不是一直阻塞
服务器代码 /*server.c*/ #include #include #include #include #include #include #include #include #define PORT 4321 #define BUFFER_SIZE 1024 #define MAX_QUE_CONN_NM 5 int main() { struct sockaddr_in server_sockaddr, client_sockaddr; int sin_size, recvbytes; int sockfd, client_fd; char buf[BUFFER_SIZE]; /*建立socket连接*/ if ((sockfd = socket(AF_INET,SOCK_STREAM,0))== -1) { perror("socket"); exit(1); } printf("Socket id = %d ",sockfd); /*设置sockaddr_in 结构体中相关参数*/ server_sockaddr.sin_family = AF_INET; server_sockaddr.sin_port = htons(PORT); server_sockaddr.sin_addr.s_addr = INADDR_ANY; bzero(&(server_sockaddr.sin_zero), 8); int i = 1;/* 使得重复使用本地地址与套接字进行绑定 */ setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &i, sizeof(i)); /*绑定函数bind*/ if (bind(sockfd, (struct sockaddr *)&server_sockaddr, sizeof(struct sockaddr))== -1) { perror("bind"); exit(1); } printf("Bind success! "); /*调用listen函数*/ if (listen(sockfd, MAX_QUE_CONN_NM) == -1) { perror("listen"); exit(1); } printf("Listening.... "); /*调用accept函数，等待客户端的连接*/ if ((client_fd = accept(sockfd, (struct sockaddr *)&client_sockaddr, &sin_size)) == -1) { perror("accept"); exit(1); } /*调用recv函数接收客户端的请求*/ memset(buf , 0, sizeof(buf)); if ((recvbytes = recv(client_fd, buf, BUFFER_SIZE, 0)) == -1) { perror("recv"); exit(1); } printf("Received a message: %s ", buf); close(sockfd); exit(0); }

客户端代码

/*client.c*/ #include #include #include #include #include #include #include #include #include #define PORT 4321 #define BUFFER_SIZE 1024 int main(int argc, char *argv[]) { int sockfd, sendbytes; char buf[BUFFER_SIZE]; struct hostent *host; struct sockaddr_in serv_addr; if(argc < 3) { fprintf(stderr,"USAGE: ./client Hostname(or ip address) Text "); exit(1); } /*地址解析函数*/ if ((host = gethostbyname(argv[1])) == NULL) { perror("gethostbyname"); exit(1); } memset(buf, 0, sizeof(buf)); sprintf(buf, "%s", argv[2]); /*创建socket*/ if ((sockfd = socket(AF_INET,SOCK_STREAM,0)) == -1) { perror("socket"); exit(1); } /*设置sockaddr_in 结构体中相关参数*/ serv_addr.sin_family = AF_INET; serv_addr.sin_port = htons(PORT); serv_addr.sin_addr = *((struct in_addr *)host->h_addr); bzero(&(serv_addr.sin_zero), 8); /*调用connect函数主动发起对服务器端的连接*/ if(connect(sockfd,(struct sockaddr *)&serv_addr, sizeof(struct sockaddr))== -1) { perror("connect"); exit(1); } /*发送消息给服务器端*/ if ((sendbytes = send(sockfd, buf, strlen(buf), 0)) == -1) { perror("send"); exit(1); } close(sockfd); exit(0); }


下面是优化后的服务器 ‘/* net_select.c */ #include #include #include #include #include #include #include #include #include #define PORT 4321 #define MAX_QUE_CONN_NM 5 #define MAX_SOCK_FD FD_SETSIZE #define BUFFER_SIZE 1024 int main() { struct sockaddr_in server_sockaddr, client_sockaddr; int sin_size, count; fd_set inset, tmp_inset; int sockfd, client_fd, fd; char buf[BUFFER_SIZE]; if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) { perror("socket"); exit(1); } server_sockaddr.sin_family = AF_INET; server_sockaddr.sin_port = htons(PORT); server_sockaddr.sin_addr.s_addr = INADDR_ANY; bzero(&(server_sockaddr.sin_zero), 8); int i = 1;/* 使得重复使用本地地址与套接字进行绑定 */ setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &i, sizeof(i)); if (bind(sockfd, (struct sockaddr *)&server_sockaddr, sizeof(struct sockaddr)) == -1) { perror("bind"); exit(1); } if(listen(sockfd, MAX_QUE_CONN_NM) == -1) { perror("listen"); exit(1); } printf("listening.... "); /*将调用socket函数的描述符作为文件描述符*/ FD_ZERO(&inset); FD_SET(sockfd, &inset); while(1) { tmp_inset = inset; sin_size=sizeof(struct sockaddr_in); memset(buf, 0, sizeof(buf)); /*调用select函数*/ if (!(select(MAX_SOCK_FD, &tmp_inset, NULL, NULL, NULL) > 0)) { perror("select"); close(sockfd); exit(1); } for (fd = 0; fd < MAX_SOCK_FD; fd++) { if (FD_ISSET(fd, &tmp_inset) > 0) { if (fd == sockfd) { /* 服务端接收客户端的连接请求 */ if ((client_fd = accept(sockfd, (struct sockaddr *)&client_sockaddr, &sin_size))== -1) { perror("accept"); exit(1); } FD_SET(client_fd, &inset); printf("New connection from %d(socket) ", client_fd); } else /* 处理从客户端发来的消息 */ { if ((count = recv(fd, buf, BUFFER_SIZE, 0)) > 0) { printf("Received a message from %d: %s ", fd, buf); } else { close(fd); FD_CLR(fd, &inset); printf("Client %d(socket) has left ", fd); } } } /* end of if FD_ISSET*/ } /* end of for fd*/ } /* end if while while*/ close(sockfd); exit(0); }

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