tcp.c

来自「支持ZModem, Telnet功能的串口通讯程序」· C语言 代码 · 共 57 行

/*
 * This function sets up a tcp call to the the machine specified in the passed
 * string. if the machine name is followed by a colon then a specific tcp
 * service may be specified, else the telnet service is used. A file descriptor
 * to and from the machine is returned or else -1.
 */

#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include "virtmodem.h"

int
call_tcp(char *c)
{
    struct in_addr sock;
    struct sockaddr_in a;
    struct hostent *entry;
    struct servent *service;
    char *servicename;
    int fd;

    /* look for alternative service names */
    servicename=strrchr(c,':');
    if(servicename) {
	*servicename='\0';
	servicename++;
    } else
	servicename="telnet";

    /* try to make a socket */
    if ((fd=socket(AF_INET, SOCK_STREAM, 0))==-1)
	return -1;

    /* get machine either by name or by IP address */
    entry=gethostbyname(c);
    if (!entry)
	sock.s_addr=inet_addr(c);
    else
	sock= *((struct in_addr *)entry->h_addr);

    /* setup the destination port */
    a.sin_family=PF_INET;
    service=getservbyname(servicename, "tcp");
    if (service==0)
	return -1;
    a.sin_port=service->s_port;
    a.sin_addr=sock;

    /* attempt the connection and return */
    if (connect(fd, (struct sockaddr *)&a, sizeof(struct sockaddr_in))==-1)
	return -1;
    return fd;
}