网站建设学,输入一组基因做网络图的网站,网站建设培训西安,wordpress 首页图片报文格式最重要的是如何确定报文的边界。常见的报文格式有两种方法#xff0c;一种是发送端把要发送的报文长度预先通过报文告知给接收端#xff1b;另一种是通过一些特殊的字符来进行边界的划分。 这篇文章中讲的是发送报文长度的方法。报文类型如下#xff1a;
第一部分…报文格式最重要的是如何确定报文的边界。常见的报文格式有两种方法一种是发送端把要发送的报文长度预先通过报文告知给接收端另一种是通过一些特殊的字符来进行边界的划分。 这篇文章中讲的是发送报文长度的方法。报文类型如下
第一部分是4个字节大小的消息长度其目的是将真正发送的字节流的大小显式通过报文告知接收端第二部分是 4 个字节大小的消息类型第2部分才是真正需要发送的数据。
发送端
readnMessageByLength.c里边的代码如下
#includestdio.h
#includestdlib.h
#includestring.h
#includeunistd.h
#includearpa/inet.h
#includesys/socket.h
#includeerrno.h
#includesyslog.h
#includesignal.h
size_t readn(int fd, void *buffer, size_t length);
size_t read_message(int fd, char *buffer, size_t length);static int count;static void sig_int(int signo) {printf(\nreceived %d datagrams\n, count);exit(0);
}int main(int argc, char **argv) {if (argc ! 2) {printf(usage: select01 IPaddress or Port\n);}int listenfd;listenfd socket(AF_INET, SOCK_STREAM, 0);struct sockaddr_in server_addr;memset(server_addr, 0, sizeof(server_addr));server_addr.sin_family AF_INET;server_addr.sin_addr.s_addr htonl(INADDR_ANY);server_addr.sin_porthtons(atoi(argv[1]));int on 1;setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, on, sizeof(on));int rt1 bind(listenfd, (struct sockaddr *) server_addr, sizeof(server_addr));if (rt1 0) {printf(bind failed);exit(errno);}int rt2 listen(listenfd, 5);if (rt2 0) {printf(listen failed);exit(errno);}signal(SIGPIPE, SIG_IGN);int connfd;struct sockaddr_in client_addr;socklen_t client_len sizeof(client_addr);if ((connfd accept(listenfd, (struct sockaddr *) client_addr, client_len)) 0) {printf(bind failed);exit(errno);}char buf[128];count 0;while (1) {int n read_message(connfd, buf, sizeof(buf));if (n 0) {printf(error read message\n);exit(errno);} else if (n 0) {printf(client closed \n);exit(0);}buf[n] 0;printf(received %d bytes: %s\n, n, buf);count;}exit(0);}size_t readn(int fd, void *buffer, size_t length) {size_t count;ssize_t nread;char *ptr;ptr buffer;count length;while (count 0) {nread read(fd, ptr, count);if (nread 0) {if (errno EINTR)continue;elsereturn (-1);} else if (nread 0)break; /* EOF */count - nread;ptr nread;}return (length - count); /* return 0 */
}size_t read_message(int fd, char *buffer, size_t length) {u_int32_t msg_length;u_int32_t msg_type;int rc;rc readn(fd, (char *) msg_length, sizeof(u_int32_t));if (rc ! sizeof(u_int32_t))return rc 0 ? -1 : 0;msg_length ntohl(msg_length);rc readn(fd, (char *) msg_type, sizeof(msg_type));if (rc ! sizeof(u_int32_t))return rc 0 ? -1 : 0;if (msg_length length) {return -1;}rc readn(fd, buffer, msg_length);if (rc ! msg_length)return rc 0 ? -1 : 0;return rc;
}gcc readnMessageByLength.c -o readnMessageByLength编译./readnMessageByLength 8080运行。
接收端
SendMessageByLength.c里边的代码如下
#includestdio.h
#includestdlib.h
#includestring.h
#includeunistd.h
#includearpa/inet.h
#includesys/socket.h
#includeerrno.h
#includesyslog.h
#includesignal.h
int main(int argc, char **argv) {if (argc ! 3) {printf(usage: tcpclient IPaddress\n);exit(errno);}int socket_fd;socket_fd socket(AF_INET, SOCK_STREAM, 0);struct sockaddr_in server_addr;bzero(server_addr, sizeof(server_addr));server_addr.sin_family AF_INET;server_addr.sin_port htons(atoi(argv[2]));;inet_pton(AF_INET, argv[1], server_addr.sin_addr);socklen_t server_len sizeof(server_addr);int connect_rt connect(socket_fd, (struct sockaddr *) server_addr, server_len);if (connect_rt 0) {fprintf(stderr, error in connect: %s (%d)\n, strerror(errno), errno);exit(errno);}struct {u_int32_t message_length;u_int32_t message_type;char buf[128];} message;int n;while (fgets(message.buf, sizeof(message.buf), stdin) ! NULL) {n strlen(message.buf);message.message_length htonl(n);message.message_type 1;if (send(socket_fd, (char *) message, sizeof(message.message_length) sizeof(message.message_type) n, 0) 0){fprintf(stderr, error in send: %s (%d)\n, strerror(errno), errno);exit(errno);}}exit(0);
}gcc SendMessageByLength.c -o SendMessageByLength编译./SendMessageByLength 127.0.0.1 8080运行。
