Sockets for Clients - Java Network Programming - page 243

String hostname = args . length > 0 ? args [ 0 ] : "time.nist.gov" ;
Socket socket = null ;
try {
socket = new Socket ( hostname , 13 );
socket . setSoTimeout ( 15000 );
InputStream in = socket . getInputStream ();
StringBuilder time = new StringBuilder ();
InputStreamReader reader = new InputStreamReader ( in , "ASCII" );
for ( int c = reader . read (); c != - 1 ; c = reader . read ()) {
time . append (( char ) c );
}
System . out . println ( time );
} catch ( IOException ex ) {
System . err . println ( ex );
} finally {
if ( socket != null ) {
try {
socket . close ();
} catch ( IOException ex ) {
// ignore
}
}
}
}
}
Typical output is much the same as if you connected with Telnet:
$ java DaytimeClient
56375 13-03-24 15:05:42 50 0 0 843.6 UTC(NIST) *
As far as network-specific code goes, that's pretty much it. In most network programs
like this, the real effort is in speaking the protocol and comprehending the data formats.
For instance, rather than simply printing out the text the server sends you, you might
want to parse it into a java.util.Date object instead. Example 8-2 shows you how to
do this. For variety, I also wrote this example taking advantage of Java 7's AutoCloseable
and try-with-resources.
Example 8-2. Construct a Date by talking to time.nist.gov
import java.net.* ;
import java.text.* ;
import java.util.Date ;
import java.io.* ;
public class Daytime {
public Date getDateFromNetwork () throws IOException , ParseException {
try ( Socket socket = new Socket ( "time.nist.gov" , 13 )) {
socket . setSoTimeout ( 15000 );
InputStream in = socket . getInputStream ();
StringBuilder time = new StringBuilder ();