I have forgotten to include some functions needed in file tel_cli.c, please append the belowed source code to the end of file tel_cli.c.


/*connectsock - allocate & connect a socket using TCP or TCP*/
int connectsock(const char *host,const char *service, const char *transport)
/* arguments:
* host --- name of host to which connection is desired
* service -- service associated with the desired port
* transport --- name of transport protocol to use ("tcp" or "udp")
*/
{
struct hostent *phe; /* pointer to host information entry */
struct servent *pse; /* pointer to service information entry */
struct protoent *ppe; /* pointer to protocol information entry */
struct sockaddr_in sin; /* an Internet endpoint addredd */
int s,type; /* socket descriptor and socket type */

memset(&sin,0,sizeof(sin));
sin.sin_family=AF_INET;

/* Map service name to port number */
if (pse = getservbyname(service,transport))
sin.sin_port = pse->s_port;
else if ((sin.sin_port = htons((u_short)atoi(service))) == 0 )
{
//errexit("can't get \"%s\" service entry\n",service);
printf("can't get \"%s\" service entry\n",service);
return 0;
}

/* Map host name to IP address,allowing for dotted decimal */
if (phe = gethostbyname(host))
memcpy(&sin.sin_addr,phe->h_addr,phe->h_length);
else if ((sin.sin_addr.s_addr = inet_addr(host)) == INADDR_NONE)
{
//errexit("can't get \"%s\" protocol entry\n",transport);
printf("can't get \"%s\" protocol entry\n",transport);
return 0;
}

/* Map transport protocol name to protocol number */
if ((ppe = getprotobyname(transport))==0)
{
//errexit("can't get \"%s\" protocol entry\n",transport);
printf("can't get \"%s\" protocol entry\n",transport);
return 0;
}

/* User protocol to choose a socket type */
if (strcmp(transport,"udp") == 0)
type = SOCK_DGRAM;
else
type = SOCK_STREAM;

/*Allocate a socket */
s = socket(PF_INET, type, ppe->p_proto);
if (s < 0)
{
//errexit("can't create socket:%s\n", strerror(errno));
printf("can't create socket:%s\n", strerror(errno));
return 0;
}
/* connect the socket */
if (connect (s,(struct sockaddr *)&sin,sizeof(sin)) < 0)
{
//errexit("can't connect to %s.%s: %s\n",host,service,strerror(errno));
printf("can't connect to %s.%s: %s\n",host,service,strerror(errno));
return 0;
}
return s;

}


int connectTCP(const char *host, const char *service)
/* arguments:
* host --- name of host to which connection is desired
* service --- service associated with the desired port
*/
{
return connectsock(host,service,"tcp");
}




/* errexit --- print an error mesage and exit */

/*VARARGS1*/

int errexit(const char *format,...)
{
va_list args;
va_start(args,format);
vfprintf(stderr,format,args);
va_end(args);
exit(1);
}