实验平台
linux
实验内容
编写UDP服务器和客户端程序,客户端发送消息,服务器接收消息,并打印客户端的IP地址和端口号。
实验原理
UDP是无需连接的通信,其主要实现过程如下:
同样,我们可以按照上一篇博客:基于TCP的客户端和服务器端的代码设计的办法,将服务器代码分成两部分,一个是初始化,一个是收发数据。但是UDP服务器初始化较为简单,也可以直接写在main函数里。
UDP和TCP在读写数据上较为不同的是,sendto()和recvfrom(),这两个函数较为复杂。通过man手册查询得到:
ssize_t sendto(int sockfd, const void *buf, size_t len, intflags,const struct sockaddr *dest_addr, socklen_t addrlen);
参数1:文件描述符;参数2:要发送的buf数据,是个指针
参数3:目的地的地址,是个指针,在使用时需要强制类型转换成(struct sockaddr *)参数4:目的地的地址长度。具体的例子看下面代码
ssize_t recvfrom(int sockfd, void *buf, size_t len, intflags,struct sockaddr *src_addr, socklen_t *addrlen);
参数1:文件描述符;参数2:要接收的buf缓冲区
参数3:接收的来源地址,在使用时需要强制类型转换成(struct sockaddr *)参数4:一个指针,指向地址长度。具体的例子看下面代码
服务器端代码:udpserver.c
#include #include#include#include#include#include#include
#define BUFFER_SIZE 100
#define PORT 1234int32_t main(int32_t argc,char *argv[])
{structsockaddr_in server;structsockaddr_in client;charbuf[BUFFER_SIZE];
int32_t len= sizeof(client);
int32_t ret= 0;
int32_t file_len= 0;if (argc != 2)
{
printf("Usage ./server [ip]\n");return -1;
}
int32_t sockfd= socket(AF_INET, SOCK_DGRAM, 0);if (sockfd < 0)
{
perror("create socket failed!");
exit(1);
}
bzero(&server, sizeof(structsockaddr_in));
server.sin_family=AF_INET;
server.sin_port= htons(PORT); /**< 主机字节序转化成网络字节序*/server.sin_addr.s_addr= inet_addr(argv[1]); /**< 字符串转换in_addr的函数*/
/**< 绑定服务器*/
if (bind(sockfd, (struct sockaddr *)&server, sizeof(server)) < 0)
{
perror("bind failed!");
exit(1);
}
ret= recvfrom(sockfd, buf, BUFFER_SIZE, 0, (struct sockaddr *)&client, &len);if (ret < 0)
{
perror("recvfrom failed!");
exit(1);
}
buf[ret]= '\0';
printf("client message: %s\n", buf);
printf("client's ip is %s, port is %d.\n", inet_ntoa(client.sin_addr), htons(client.sin_port));/**< 向客户端发送信息*/
if (sendto(sockfd, "Welcome to server", BUFFER_SIZE, 0, (struct sockaddr *)&client, len) < 0)
{
perror("send file len to client error");
}
close(sockfd);return 0;
}
客户端代码:udpclient.c
#include #include#include#include#include#include#include
#define BUFFER_SIZE 100
#define PORT 1234int32_t main(int argc,char *argv[])
{structsockaddr_in server;structsockaddr_in peer;charbuf[BUFFER_SIZE];
int32_t len= sizeof(peer);char sendbuf[BUFFER_SIZE] = "welcome to client";
int32_t num= 0;if (argc != 2)
{
printf("Usage ./client ip\n");
exit(1);
}int sockfd = socket(AF_INET, SOCK_DGRAM, 0);if (sockfd < 0)
{
perror("create socket failed!");
exit(1);
}
bzero(&server, sizeof(structsockaddr_in));
server.sin_family=AF_INET;
server.sin_port=htons(PORT);
server.sin_addr.s_addr= inet_addr(argv[1]);if (sendto(sockfd, sendbuf, BUFFER_SIZE, 0, (struct sockaddr *)&server, sizeof(server)) < 0)
{
perror("sendto socket failed!");
exit(1);
}if ((num = recvfrom(sockfd, buf, BUFFER_SIZE, 0, (struct sockaddr *)&peer, &len)) < 0)
{
perror("recvfrom socket failed!");
exit(1);
}
buf[num]= '\0';
printf("Server Message: %s\n", buf);
close(sockfd);return 0;
}
Makefile
all:server client
server:udpserver.c
gcc udpserver.c-o server
client:udpclient.c
gcc udpclient.c-o client
clean:
rm-rf server client
实验结果