#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <unistd.h>
#define MAXLINE 80
#define SERV_PORT 1234
void do_cli(FILE *fp, int sockfd, struct sockaddr *pservaddr, socklen_t servlen)
{
int n;
char sendline[MAXLINE], recvline[MAXLINE + 1];
/* connect to server */
if(connect(sockfd, (struct sockaddr *)pservaddr, servlen) == -1)
{
perror("connect error");
exit(1);
}
while(fgets(sendline, MAXLINE, fp) != NULL)
{
/* read a line and send to server */
write(sockfd, sendline, strlen(sendline));
/* receive data from server */
n = read(sockfd, recvline, MAXLINE);
if(n == -1)
{
perror("read error");
exit(1);
}
recvline[n] = 0; 
/* terminate string */
fputs(recvline, stdout);
}
}

int main(int argc, char **argv)
{
int sockfd;
struct sockaddr_in servaddr;
/* check args */
if(argc != 2)
{
printf("usage: udpclient <IPaddress>\n");
exit(1);
}
/* init servaddr */
bzero(&servaddr, 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("[%s] is not a valid IPaddress\n", argv[1]);
exit(1);
}
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
do_cli(stdin, sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
return 0;
}