UDP c/s 模型

server.c

/* udp server.c */
#include <string.h>
#include <netinet/in.h>
#include <stdio.h>
#include <unistd.h>
#include <strings.h>
#include <arpa/inet.h>
#include <ctype.h>
#define MAXLINE 80
#define SERV_PORT 8000
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, );
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(SERV_PORT);
bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
printf("Accepting connections ...\n");
while () {
cliaddr_len = sizeof(cliaddr);
n = recvfrom(sockfd, buf, MAXLINE,, (struct sockaddr *)&cliaddr, &cliaddr_len);
if (n == -)
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 = ; i < n; i++)
buf[i] = toupper(buf[i]);
n = sendto(sockfd, buf, n, , (struct sockaddr *)&cliaddr, sizeof(cliaddr));
if (n == -)
perror("sendto error");
}
close(sockfd);
return ;
}

client.c

/* udp client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <strings.h>
#include <ctype.h>
#define MAXLINE 80
#define SERV_PORT 8000
int main(int argc, char *argv[])
{
struct sockaddr_in servaddr;
int sockfd, n;
char buf[MAXLINE];
sockfd = socket(AF_INET, SOCK_DGRAM, );
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
servaddr.sin_port = htons(SERV_PORT);
while (fgets(buf, MAXLINE, stdin) != NULL) {
n = sendto(sockfd, buf, strlen(buf), , (struct sockaddr *)&servaddr, sizeof(servaddr));
if (n == -)
perror("sendto error");
n = recvfrom(sockfd, buf, MAXLINE, , NULL, );
if (n == -)
perror("recvfrom error");
write(STDOUT_FILENO, buf, n);
}
close(sockfd);
return ;
}