UDP客户端使用connect与UDP服务器使用send函数和recv函数收发数据

服务器代码编译运行

服务器udpconnectToServer.c的代码如下：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<arpa/inet.h>
#include<sys/socket.h>
#include<errno.h>
#include<syslog.h> 
#include<signal.h>
#define    MAXLINE     4096static int count;static void quitHere(int signo) {printf("\nreceived %d datagrams\n", count);exit(0);
}int main(int argc, char **argv) {int socket_fd;socket_fd = socket(AF_INET, SOCK_DGRAM, 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_port = htons(atoi(argv[1]));bind(socket_fd, (struct sockaddr *) &server_addr, sizeof(server_addr));socklen_t client_len;char message[MAXLINE];message[0] = 0;count = 0;signal(SIGINT, quitHere);struct sockaddr_in client_addr;client_len = sizeof(client_addr);// recvfrom会把客户端返回对端发送方的地址和端口等信息放到client_addr和client_len中int n = recvfrom(socket_fd, message, MAXLINE, 0, (struct sockaddr *) &client_addr, &client_len);if (n < 0) {fprintf(stderr, "error in recvfrom function: %s (%d)\n", strerror(errno), errno);}message[n] = 0;printf("received length is %d bytes \ncontent: %s\n", n, message);if (connect(socket_fd, (struct sockaddr *) &client_addr, client_len)) {fprintf(stderr, "connect error: %s (%d)\n", strerror(errno), errno);}while (strncmp(message, "quit", 4) != 0) {char send_line[MAXLINE];sprintf(send_line, "Hi, %s", message);size_t rt = send(socket_fd, send_line, strlen(send_line), 0);if (rt < 0) {fprintf(stderr, "send error: %s (%d)\n", strerror(errno), errno);}printf("send bytes: %zu \n", rt);size_t rc = recv(socket_fd, message, MAXLINE, 0);if (rc < 0) {fprintf(stderr, "recv error: %s (%d)\n", strerror(errno), errno);}count++;}exit(0);
}

gcc udpconnectserver.c -o udpconnectserver进行编译，./udpconnectserver 8080运行。

客户端代码编译与运行

客户端udpconnectToServer.c的代码如下：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<arpa/inet.h>
#include<sys/socket.h>
#include<errno.h>
#include<syslog.h>
# define    MAXNUMBER     4096int main(int argc, char **argv) {if (argc != 3) {printf("usage: udpclient1 <IPaddress> or <Port>");}int socket_fd;socket_fd = socket(AF_INET, SOCK_DGRAM, 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);if (connect(socket_fd, (struct sockaddr *) &server_addr, server_len)) {printf("fail in connect");exit(1);}struct sockaddr *reply_addr;reply_addr = malloc(server_len);char sendLine[MAXNUMBER], receiveLine[MAXNUMBER + 1];socklen_t len;int n;while (fgets(sendLine, MAXNUMBER, stdin) != NULL) {int i = strlen(sendLine);if (sendLine[i - 1] == '\n') {sendLine[i - 1] = 0;}printf("send Content: %s\n", sendLine);size_t rt = send(socket_fd, sendLine, strlen(sendLine), 0);if (rt < 0) {printf("error in sending");}printf("send Content's bytes: %zu \n", rt);len = 0;receiveLine[0] = 0;n = recv(socket_fd, receiveLine, MAXNUMBER, 0);if (n < 0){if (errno){fprintf(stderr, "error in recvfrom: %s (%d)\n", strerror(errno), errno);}else{printf("recvfrom not success");}}receiveLine[n] = 0;fputs(receiveLine, stdout);fputs("\n", stdout);}exit(0);
}

gcc udpconnectToServer.c -o udpconnectToServer进行编译，./udpconnectToServer 127.0.0.1 8080运行。

实验

这里打开两个终端，然后连接到同一个机器上边。
然后在客户端发送一条信息good,可以看到服务器上收到了good并且给客户端发送了Hi, good。

以quit开头的字符串从客户端发送过来之后，就会让服务器关闭。

此文章为11月Day 23学习笔记，内容来源于极客时间《网络编程实战》。