InetAddress host;
int port = DEFAULT_PORT;
try {
if (args.length > 0) {
host = InetAddress.getByName(args[0]);
}
else {
host = InetAddress.getByName(DEFAULT_HOST);
}
}
catch (Exception ex) {
System.out.println("Usage: java UDPTimeClient host port");
return;
}
if (args.length > 1) {
try {
port = Integer.parseInt(args[1]);
if (port <= 0 || port > 65535) port = DEFAULT_PORT;;
}
catch (Exception ex){
}
}
try {
UDPPoke poker = new UDPPoke(host, port);
byte[] response = poker.poke();
if (response == null) {
System.out.println("No response within allotted time");
return;
}
else if (response.length != 4) {
System.out.println("Unrecognized response format");
return;
}
// The time protocol sets the epoch at 1900,
// the Java Date class at 1970. This number
// converts between them.
long differenceBetweenEpochs = 2208988800L;
long secondsSince1900 = 0;
for (int i = 0; i < 4; i++) {
secondsSince1900
= (secondsSince1900 << 8) | (response[i] & 0x000000FF);
}
long secondsSince1970
= secondsSince1900 - differenceBetweenEpochs;
long msSince1970 = secondsSince1970 * 1000;
Date time = new Date(msSince1970);
System.out.println(time);
}
catch (Exception ex) {
System.err.println(ex);
ex.printStackTrace();
}
