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tcp_time_client.c
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C/C++ Source or Header
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2004-05-03
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11KB
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345 lines
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <string.h>
#include <ctype.h>
main(argc,argv)
int argc;
char *argv[];
{
/*
client process to connect to the daytime service via port 13.
The client process uses the time message received to check (and
optionally to set) the time of the local clock. the comparison
assumes that the local clock keeps time in seconds from 1/1/70
which is the UNIX standard, and it computes the time difference
by converting the received MJD to seconds since 1/1/70 and adding
the received hr, min and sec, also converted to seconds. If the
local machine keeps time in some other way, then the comparison
method will have to change, but the rest should be okay.
This software was developed with US Government support
and it may not be sold, restricted or licensed. You
may duplicate this program provided that this notice
remains in all of the copies, and you may give it to
others provided they understand and agree to this
condition.
This program and the time protocol it uses are under
development and the implementation may change without
notice.
For questions or additional information, contact:
Judah Levine
Time and Frequency Division
NIST/847
325 Broadway
Boulder, Colorado 80305
(303) 492 7785
jlevine@boulder.nist.gov
*/
long int address; /* holds ip address */
int pserv = 13; /* daytime port number on server */
char *cp; /* server address in . notation */
char *sp; /* temporary for server address*/
int aindots[4]; /* numerical host address in dot notation*/
char addrbuf[20]; /* address formatted into dot notation*/
int j;
struct sockaddr_in sin; /* socket address structure */
int s; /* socket number */
int length; /* size of message */
char buf[132]; /* holds message */
long int mjd0 = 40587; /* MJD of 1/1/70 = origin of UNIX time system*/
struct timeval tvv,tgg; /* holds local time */
long int mjd; /* holds parsed received mjd*/
int yr,mo,dy,hr,min,sec; /* holds parsed received time */
int dst,ls,health; /* received flags: dst, ls and health */
long int diff; /* time difference, local - NIST */
char cc;
int stat;
int sw(); /*parses command-line switches*/
char let; /*command-line letter*/
long int val; /*command line value*/
struct hostent *serv0; /*pointer to structure returned by gethost */
/*
the following variables define what this program
should do and what output should be produced. The
values below are the defaults which may be changed
by characters on the command line as described below.
The effect of each variable is as follows:
Command-Line Switch effect
-m0 msg = 0 Do not produce any messages;
only time difference is written to
standard output.
-m1 or -M = 1 Produce short messages.
-m2 = 2 Produce longer messages.
-s0 set = 0 Do not adjust local time.
-s1 or -S = 1 Adjust local time if server is healthy.
-s2 = 2 Adjust local time even if server is
unhealthy.
-s3 = 3 Ask operator first.
-u<j> use server number j, where j is the index number
of the NIST server chosen from the following list.
the first server on the list is number 1, the
second is number 2, etc.
the default is to use the first server, which
is number 1.
note that the array uses C indexing, so that the
first entry in the array is number 0, etc.
thus any user response is decremented before
being used.
-u0 the name of the server is given as the next
parameter on the command line. the name can
be either a name or an ip address in dot
notation. The entry will be taken as a name
if the first non-blank character is not a
digit.
*/
int msg =1; /*default is short messages */
int set =3; /*default is ask before setting clock */
int use_serv=0; /*use server 1 by default*/
/*
the following is a list of the servers operated by
NIST. All of them will support the daytime protocol
in the format that this program expects.
Each server may be specified either by name, as in
time.nist.gov or by ip as in 192.43.244.18. If the
first character of the specification is a digit, then
the numerical format is assumed. If a name is entered,
it is converted to the corresponding ip address using
the standard DNS query. The program will fail if the
DNS query cannot find the ip number of the server
For more information about these servers, look at the
entry for the Internet Time Service on the Time and
Frequency Division homepage at www.boulder.nist.gov/timefreq
*/
#define NUMSRV 15
char *serv_ip[NUMSRV]= {"64.236.96.53" ,/*nist1.aol-va.truetime.com*/
"128.138.140.44" ,/*utcnist.colorado.edu*/
"207.200.81.113" ,/*nist1.aol-ca.truetime.com*/
"216.200.93.8" ,/*nist1-dc.glassey.com*/
"63.149.208.50" ,/*nist1.datum.com*/
"208.184.49.9" ,/*nist1-ny.glassey.com*/
"207.126.103.204",/*nist1-sj.glassey.com*/
"129.6.15.28" ,/*time-a.nist.gov*/
"129.6.15.29" ,/*time-b.nist.gov*/
"132.163.4.101" ,/*time-a.timefreq.bldrdoc.gov*/
"132.163.4.102" ,/*time-b.timefreq.bldrdoc.gov*/
"132.163.4.103" ,/*time-c.timefreq.bldrdoc.gov*/
"192.43.244.18" ,/*time.nist.gov*/
"131.107.1.10" ,/*time-nw.nist.gov*/
"utcnist.colorado.edu"/*DNS entry =128.138.140.44*/
};
/*
parse command line
*/
while( sw(argc,argv,&let,&val) != 0) /*switch is present*/
{
switch(let)
{
case 'm':
msg=val;
break;
case 's':
set=val;
break;
case 'S':
set=1;
break;
case 'M':
msg=1;
break;
case 'u': /*specifies which server to use*/
if(val == 0) /*next parameter specifies server*/
{
argc--;
argv++; /*skip over the switch*/
if(argc <= 1)
{
printf("\n Expected server name is missing.\n\n");
exit();
}
cp=argv[1]; /*save the next parameter as the server name*/
use_serv=999; /*set flag*/
break;
}
/* server 1 has internal index 0 */
use_serv=val-1;
/* check if entry is out of range*/
if(use_serv < 0) use_serv=0;
if(use_serv >= NUMSRV) use_serv=NUMSRV - 1;
break;
default:
fprintf(stderr,"\nSwitch %c not recognized.",let);
break;
}
argc--; /*decrement argument counter */
argv++; /*and increment pointer */
}
/*
get internet address of selected server
if the first digit is not a digit then lookup
the host name and get its ip address. the program
will fail and exit if the name cannot be resolved.
*/
if(use_serv != 999) cp=serv_ip[use_serv];
if(!isdigit(*cp)) /*first char not a digit, must convert name*/
{
if( (serv0=gethostbyname(cp)) == NULL)
{
printf("\n Cannot resolve name %s",cp);
exit();
}
if(serv0->h_length != 4)
{
printf("\nLength of host address (= %d) is wrong, 4 expected.",
serv0->h_length);
exit();
}
sp= serv0->h_addr_list[0];
for(j=0; j<4; j++) /*store and convert address*/
{
aindots[j]= *(sp++);
aindots[j] &= 0xff; /*turn off sign extension*/
}
sprintf(addrbuf,"%d.%d.%d.%d",
aindots[0],aindots[1],aindots[2],aindots[3]);
cp= addrbuf;
}
printf("\n Using server at address %s",cp);
/*
convert address to internal format
*/
if( (address=inet_addr(cp) ) == -1)
{
fprintf(stderr,"\n Internet address error.");
exit(1);
}
bzero( (char *)&sin,sizeof(sin));
sin.sin_addr.s_addr=address;
sin.sin_family=AF_INET;
sin.sin_port=htons(pserv);
/*
create the socket and then connect to the server
note that this is a stream socket and that record
boundaries are not preserved.
*/
if( (s=socket(AF_INET,SOCK_STREAM,0) ) < 0)
{
fprintf(stderr,"\n Socket creation error.");
exit(1);
}
if(connect(s, (struct sockaddr *) &sin, sizeof(sin) ) < 0)
{
perror(" time server Connect failed --");
exit(1);
}
length=read(s,buf,80);
gettimeofday(&tvv,0); /*get time as soon as read completes*/
if(length <= 0)
{
fprintf(stderr,"\n No response from server.");
close(s);
exit(1);
}
buf[length]= '\0'; /*add terminating null */
if(msg != 0)
{
printf("\n Time message received:");
printf("\n D L");
printf("\n MJD YY MM DD HH MM SS ST S H Adv.");
printf("%s\n",buf);
}
close(s);
/*
now compute difference between local time and
received time.
*/
sscanf(buf," %ld %2d-%2d-%2d %2d:%2d:%2d %d %d %d",
&mjd,&yr,&mo,&dy,&hr,&min,&sec,&dst,&ls,&health);
if(msg == 2) /*longer messages selected */
{
if( (dst == 0) || (dst > 51) )
{
printf("\nStandard Time now in effect.");
if(dst > 51)
printf("\nChange to Daylight Saving Time in %d days.",dst-51);
}
if( (dst <= 50) && (dst > 1) )
{
printf("\nDaylight Saving Time now in effect.");
if( (dst > 1) && (dst < 50) )
printf("\nChange to Standard Time in %d days.",dst-1);
}
if(dst == 1) printf("\nStandard time begins at 2am today.");
if(dst == 51)printf("\nDaylight Saving Time begins at 2am today.");
if(ls ==1) printf("\nLeap Second to be added at end of month.");
if(ls ==2) printf("\nSecond to be dropped at end of month.");
}
/*
convert received time to seconds since 1/1/70 and subtract
this from the local time in the same units.
Since no correction has been made for the network delay,
this difference cannot be taken too seriously, although
the delay in a local network should be no more than about
0.05 seconds.
*/
diff=tvv.tv_sec - 86400*(mjd-mjd0) - 3600*hr -60*min - sec;
if(tvv.tv_usec >= 500000l) diff++; /*round microseconds */
if(msg == 0) /*no messages except time diff.*/
printf("%ld",diff);
else
printf("\nLocal Clock - NIST = %ld second(s).",diff);
if(diff == 0)
{
if(msg != 0) printf("\n No adjustment is needed.\n");
exit(0);
}
if(set == 0) exit(0);
if( (health != 0) && (msg != 0) )
printf("\n Server is not healthy, adjustment not recommended.");
cc = 'n'; /*default is not to set */
if(set == 3) /*action depends on answer to query*/
{
printf("\n Do you want to adjust the local clock ? [y/n] ");
cc=getchar();
}
if( (set == 2) || /*always set */
( (set == 1) && (health == 0) ) || /*set if healthy*/
(cc == 'y') || /*set if response yes*/
(cc == 'Y') )
{
if(diff > 2100l)
{
printf("\n Adjustment limited to -2100 s.");
diff= 2100l;
}
if(diff < -2100l)
{
printf("\n Adjustment limited to +2100 s.");
diff= -2100l;
}
tvv.tv_sec= -diff;
tvv.tv_usec = 0;
stat=adjtime(&tvv,&tgg);
if(msg != 0)
{
if(stat == 0) printf("\n Adjustment was started.\n");
else perror("Adjustment failed. ");
}
}
exit(0);
}