基於UDP協議的網絡程序

服務器

#include <stdio.h> 
#include <string.h> 
#include <netinet/in.h> 
 
#define MAXLINE 80 
#define SERV_PORT 4101 
 
int main(void) 
{
	struct sockaddr_in servaddr, cliaddr;
	socklen_t cliaddr_len;
	int sockfd;
	char buf[MAXLINE];
	char str[INET_ADDRSTRLEN];
	int i, n;

	sockfd = socket(AF_INET, SOCK_DGRAM, 0);
	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);	/* INADDR_ANY就是指定地址爲0.0.0.0的地址,表示不確定地址,或“所有地址”、“任意地址”。*/
	servaddr.sin_port = htons(SERV_PORT);

	bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
	printf("Accepting connections ...\n");
	while (1) {
		cliaddr_len = sizeof(cliaddr);
		n = recvfrom(sockfd, buf, MAXLINE, 0, (struct scockaddr *)&cliaddr, &cliaddr_len);
		if (n == -1)
			perror("recvfrom error");
		printf("received from %s at PORT %d\n", inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)), ntohs(cliaddr.sin_port));
		for (i = 0; i < n; i++)
			buf[i] = toupper(buf[i]);
		n = sendto(sockfd, buf, n, 0, (struct sockaddr *)&cliaddr, sizeof(cliaddr));
		if (n == -1)
			perror("sendto error");
	} 

	return 0;
}

客戶端

#include <stdio.h> 
#include <string.h> 
#include <unistd.h> 
#include <netinet/in.h>
 
#define MAXLINE 80 
#define SERV_PORT 4101 
 
int main(int argc, char *argv[]) 
{
	struct sockaddr_in servaddr;
	int sockfd, n;
	char buf[MAXLINE];
	socklen_t servaddr_len;

	sockfd = socket(AF_INET, SOCK_DGRAM, 0); 

	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	inet_pton(AF_INET, "192.168.3.36", &servaddr.sin_addr);
	servaddr.sin_port = htons(SERV_PORT);

	while (fgets(buf, MAXLINE, stdin) != NULL) {
		servaddr_len = sizeof(servaddr);
		n = sendto(sockfd, buf, strlen(buf), 0, (struct sockaddr *)&servaddr, sizeof(servaddr));
		if (n == -1)
			perror("sendto error"); 

		n = recvfrom(sockfd, buf, MAXLINE, 0, (struct sockaddr *)&servaddr, &servaddr_len);
		if (n == -1)
			perror("recvfrom error");
		write(STDOUT_FILENO, buf, n);
	} 

	close(sockfd);
	return 0;
}