client.c

linux环境下网络编程的example代码

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>

#define PORT 3490 /* the port client will be connecting to */
#define MAXDATASIZE 100 /* max number of bytes we can get at once */

int main(int argc, char *argv[])
{
int sockfd, numbytes;
char buf[MAXDATASIZE] ;
struct hostent *he;
struct sockaddr_in their_addr; /* connector's address information */

if (argc != 2) {
fprintf ( stderr,"usage: client hostname\n");
exit ( 1 ) ;
  }

if ((he=gethostbyname(argv[1])) == NULL) { /* get the host info */
herror ( " gethostbyname " ) ;
exit ( 1 ) ;
}

if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
perror ( " socket " ) ;
exit ( 1 ) ;
}

their_addr.sin_family = AF_INET;
their_addr.sin_port = htons(PORT);
their_addr.sin_addr = *((struct in_addr *)he->h_addr); //inet_addr

if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof(struct sockaddr)) == -1) {
perror ( " connect " ) ;
exit ( 1 ) ;
}

if ((numbytes=recv(sockfd, buf, MAXDATASIZE, 0)) == -1) {
perror ( " recv " ) ;
exit ( 1 ) ;
}
buf[numbytes] = '\0';
printf("Received: %s",buf);
close ( sockfd ) ;
return 0;
}