Communicating Across the Internet - Java 6 - page 456

LISTING 17.2 Continued

32: }
33: digit.close();
34: } catch (IOException e) {
35: System.out.println(“IO Error:” + e.getMessage());
36: }
37: }
38: }

When making a finger request, specify a username followed by an at sign (“@”) and a
hostname, the same format as an email address. One famous real-life example is johnc@
idsoftware.com , the finger address of id Software founder John Carmack. You can
request his .plan file by running the Finger application as follows:

java Finger [e-mail]

If johnc has an account on the idsoftware.com finger server, the output of this program
is his .plan file and perhaps other information (though it appears he's no longer updat-
ing it). The server also lets you know whether a user can't be found.

Blues News includes addresses for other game designers who provide .plan updates
such as id Software developer Timothee Besset ( [e-mail] ).

The Finger application uses the StringTokenizer class to convert an address in
user @ host format into two String objects: user and host (lines 10-13).

The following socket activities are taking place:

Lines 19-20 —A new Socket is created using the hostname and port 79, the port
traditionally reserved for finger services, and a timeout of 20 seconds is set.

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Line 21 —The socket is used to get an OutputStream , which feeds into a new
PrintStream object.

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Line 22 —The finger protocol requires that the username be sent through the
socket, followed by a carriage return ('\015') and linefeed ('\012'). This is handled
by calling the print() method of the new PrintStream .

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Lines 23-24 —After the username has been sent, an input stream must be created
on the socket to receive input from the finger server. A BufferedReader stream,
in , is created by combining several stream-creation expressions together. This
stream is well suited for finger input because it can read a line of text at a time.

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Lines 26-32 —The program loops as lines are read from the buffered reader. The
end of output from the server causes in.readLine() to return null , ending the
loop.

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