Using Java to Query a Server for the Time

Question

I want to ask a server, whose IP I know, to send the date and time to a client.

How can I implement this in Java?

Answer 1

Article describing the details: http://www.informit.com/articles/article.aspx?p=26316&seqNum=3

client http://commons.apache.org/net/apidocs/org/apache/commons/net/ntp/NTPUDPClient.html

Answer 2

To start with you'll need to clarify (for yourself as much as anything):

• What kind of server are you going to ask?
• How are you going to ask it?
• What kind of IP are you expecting the server to know about?
• How would the server know about that IP?
• What does it look like for an IP to 'respond'?
• How would the server know that an IP 'responded'?
• How would the server store the knowledge of the IP responding?

Once you've answered those questions, (and more I'm sure), it'll be easier to answer how to do it in java.

Update

The updated question is much clearer.. nice.

Answer 3

Your question is not clear so I'll post a number of possible answers.

If the server exists and have a protocol to answer your request

• A1. Create a program ( probably using Sockets ) to query that server.

If the server exists but doesn't have a protocol to answer your request and YOU own that server and already logs ...which IP has been known to respond the date and time

• A2. Read those logs in the server ( probably using InputStreamReader ) Create the protocol answer the request ( Socket ) and then go to A1.

If the server exists but doesn't have a protocol to answer your request and you own that server and doesn't logs ...which IP has been known to respond the date and time

• A3. Forget it

If The server exists but doesn't have a protocol to answer your request and you DON'T own that server.

• A4. Go to A3

If the server doesn't exists and you can create it.

• A5 Create the server code and then go to A2

If the server doesn't exist and you cannot create it

• A6 Go to A3

... And so on.