网络编程学习笔记(recvfrom和sendto函数)

#include <sys/socket.h>

ssize_t recvfrom(int sockfd, void *buff, size_t nbytes, int flags, struct sockaddr *from, socklen_t *addrlen);

ssize_t sendto(int sockfd, void *buff, size_t nbytes, const struct sockaddr* to, socklen_t addrlen);

#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#define SERV_PORT 9999
#define BUF_LEN 128

void dg_echo(int sockfd, struct sockaddr_in *pcliaddr, socklen_t clilen)
{
char buf[BUF_LEN];
socklen_t len;
int n;

for (;;) {
len = clilen;
if ((n = recvfrom(sockfd, buf, BUF_LEN, 0, (struct sockaddr*)pcliaddr, &len)) < 0) {
printf("recvfrom error:%s\n", strerror(errno));
continue;
}

sendto(sockfd, buf, n, 0, (struct sockaddr*)pcliaddr, len);

}
}

int main(int argc, char **argv)
{
struct sockaddr_in servaddr, clientaddr;
int sockfd;

sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd < 0) {
printf("socket error:%s\n", strerror(errno));
return -1;
}

memset(&servaddr, 0x00, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(SERV_PORT);

if (bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0) {
printf("bind error:%s\n", strerror(errno));
close(sockfd);
return -1;
}

dg_echo(sockfd, &clientaddr, sizeof(clientaddr));
return 0;
}

#include <sys/socket.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <netinet/in.h>

#define SERV_PORT 9999
#define BUF_LEN 128

void dg_cli(FILE *fp, int sockfd, const struct sockaddr_in * pservaddr, socklen_t servlen)
{
int n;
char sendline[BUF_LEN], recvline[BUF_LEN];

while (fgets(sendline, BUF_LEN, fp) != NULL) {
sendto(sockfd, sendline, strlen(sendline), 0, (struct sockaddr*)pservaddr, servlen);
n = recvfrom(sockfd, recvline, BUF_LEN, 0, NULL, NULL);
recvline
= 0;
fputs(recvline, stdout);
}
}

int main(int argc, char **argv)
{
struct sockaddr_in servaddr;
int sock;

memset(&servaddr, 0x00, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);

if (inet_pton(AF_INET, argv[1], &servaddr.sin_addr) < 0) {
printf("inet_pton error:%s\n", strerror(errno));
return -1;
}

sock = socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0) {
printf("socket error:%s\n", strerror(errno));
return -1;
}

dg_cli(stdin, sock, &servaddr, sizeof(servaddr));
return 0;
}