talker.c

socket编程 客户端和服务器充分理解cs结构

/*
** talker.c -- a datagram "client" demo
*/

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

#define MYPORT 4950    // the port users will be connecting to

int main(int argc, char *argv[])
{
    int sockfd;
    struct sockaddr_in their_addr; // connector's address information
    struct hostent *he;
    int numbytes;
    char send_buf[256];

    /* parameters check */
    if (argc != 2) {
        fprintf(stderr,"usage: talker hostname\n");
        exit(1);
    }

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

    /* setup socket */
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
        perror("socket");
        exit(1);
    }
    
    /* receive string from console and send it to the server */
    while(1)
    {
	char * ptr;
        their_addr.sin_family = AF_INET;     // host byte order
        their_addr.sin_port = htons(MYPORT); // short, network byte order
        their_addr.sin_addr = *((struct in_addr *)he->h_addr);
        memset(&(their_addr.sin_zero), '\0', 8);  // zero the rest of the struct

	/* get string from console */
	printf("send to server:");
	ptr = send_buf;
	do
	{
		*ptr = getchar();
		ptr ++;
	}while(*(ptr-1) != '\n');
	*ptr = 0;

	/* send the string to server */
        if ((numbytes=sendto(sockfd, send_buf, strlen(send_buf), 0,
		     (struct sockaddr *)&their_addr, sizeof(struct sockaddr))) == -1) {
            perror("sendto");
            exit(1);
        }
    }

    close(sockfd);

    return 0;
}