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online courses</a></font><br x="7"><img src="imagemaster/masthead.jpg" alt="Building a Java chat server"></td><td width="*" valign="bottom" align="right"><a border="0" href="j-chat.zip"><img alt="Download tutorial zip file" border="0" src="../i/icon-zip.gif"></a><a border="0" href="j-chat-ltr.pdf"><img alt="View letter-sized PDF file" border="0" src="../i/icon-pdf-ltr.gif"></a><a border="0" href="j-chat-a4.pdf"><img alt="View A4-sized PDF file" border="0" src="../i/icon-pdf-a4.gif"></a><a href="javascript:void newWindow()" border="0"><img alt="E-mail this tutorial to a friend" border="0" src="../i/icon-email.gif"></a></td></tr><tr><td height="2" colspan="2"><img height="2" width="1" src="http://www.ibm.com/i/c.gif"></td></tr></table><TABLE border="0" cellpadding="0" cellspacing="0" width="100%"><TR><TD width="150" height="1" bgcolor="#000000" colspan="6"><IMG alt="" height="1" width="150" src="http://www.ibm.com/i/c.gif"></TD></TR><TR><TD background="../i/sw-gold.gif"><a border="0" href="index.html" onMouseOver="iOver('topmain'); iOver('bottommain'); self.status=mainblurb; return true;" onMouseOut="iOut('topmain'); iOut('bottommain'); self.status=''; return true;"><img alt="Main menu" border="0" src="../i/main.gif" name="topmain"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topsection'); iOver('bottomsection'); self.status=sectionblurb; return true;" onMouseOut="iOut('topsection'); iOut('bottomsection'); self.status=''; return true;" href="index6.html"><img alt="Section menu" border="0" src="../i/section.gif" name="topsection"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topfeedback'); iOver('bottomfeedback'); self.status=feedbackblurb; return true;" onMouseOut="iOut('topfeedback'); iOut('bottomfeedback'); self.status=''; return true;" href="j-chat-11-3.html"><img alt="Give feedback on this tutorial" border="0" src="../i/feedback.gif" name="topfeedback"></a></TD><TD width="100%" background="../i/sw-gold.gif"><img src="http://www.ibm.com/i/c.gif"></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topprevious'); iOver('bottomprevious'); self.status=previousblurb; return true;" onMouseOut="iOut('topprevious'); iOut('bottomprevious'); self.status=''; return true;" href="j-chat-6-1.html"><img alt="Previous" border="0" src="../i/previous.gif" name="topprevious"></a></TD><TD background="../i/sw-gold.gif"><img border="0" src="../i/xnext.gif"></TD></TR><TR><TD width="100%" colspan="5"></TD><TD width="108" height="1" bgcolor="#000000" align="right"><IMG alt="" height="1" width="108" src="http://www.ibm.com/i/c.gif"></TD></TR><TR><TD colspan="5"></TD><TD align="right"><a border="0" onMouseOver="iOver('topnextsection'); iOver('bottomnextsection'); self.status=nextsectionblurb; return true;" onMouseOut="iOut('topnextsection'); iOut('bottomnextsection'); self.status=''; return true;" href="j-chat-7-1.html"><img alt="Next Section" src="../i/nextsection.gif" border="0" name="topnextsection"></a></TD></TR></TABLE><table bgcolor="ffffff" cellspacing="0" cellpadding="2" border="0" height="400" width="100%"><tr valign="bottom"><a name="navskip"></a><td height="25" colspan="4"><img border="0" height="25" width="562" src="imagemaster/titlebar6.jpg" alt="6. The While-Read/Write loop (Server side)"></td></tr><tr><td bgcolor="ffffff" width="15">&nbsp;</td><td bgcolor="ffffff" width="12">&nbsp;</td><td valign="top" align="left" bgcolor="ffffff" width="*"><p><br x="7"><table cellspacing="0" cellpadding="0" border="0"><tr><td width="90%"><font size="4" face="Verdana, Arial, Helvetica"><b>The loop</b></font></td><td width="200" align="right"><font size="1" face="Verdana, Arial, Helvetica"><nobr>    page 2 of 2</nobr></font></td></tr></table><br x="7"><br x="7"></p><font size="2" face="Verdana, Arial, Helvetica"><p>So now we get to our central server loop -- this is the code that
does the real chat work. Let's take a look:</p><pre><code style="font-family: Courier New, Courier, monospace; font-size: 12">
  // This runs in a separate thread when start() is called in the
  // constructor.
  public void run() {

    try {

      // Create a DataInputStream for communication; the client
      // is using a DataOutputStream to write to us
      DataInputStream din = new DataInputStream( socket.getInputStream() );

      // Over and over, forever ...
      while (true) {

        // ... read the next message ...
        String message = din.readUTF();

        // ... tell the world ...
        System.out.println( "Sending "+message );

        // ... and have the server send it to all clients
        server.sendToAll( message );
      }
    } catch( EOFException ie ) {

      // This doesn't need an error message
    } catch( IOException ie ) {

      // This does; tell the world!
      ie.printStackTrace();
    } finally {

      // The connection is closed for one reason or another,
      // so have the server dealing with it
      server.removeConnection( socket );
    }
  }
</code></pre><p>You'll notice that we're now using our Server object in a couple of
places.</p><p>The first place is when we call <code style="font-family: Courier New, Courier, monospace; font-size: 12">server.sendToAll()</code>. This is really
just a convenience function. We could just as well have asked the server
for an Enumeration of all the OutputStreams connected to the other
side, and then written the message to each of these streams. But
because that is so frequently done, we moved the code for all of that
work to the Server object, into a method called <code style="font-family: Courier New, Courier, monospace; font-size: 12">sendToAll()</code>.</p><p>The second place we use our Server object is mentioned in the next
section.</p><br x="7"></font></td></tr></table><TABLE border="0" cellpadding="0" cellspacing="0" width="100%"><TR><TD align="right" colspan="6"><a border="0" onMouseOver="iOver('topnextsection'); iOver('bottomnextsection'); self.status=nextsectionblurb; return true;" onMouseOut="iOut('topnextsection'); iOut('bottomnextsection'); self.status=''; return true;" href="j-chat-7-1.html"><img alt="Next Section" src="../i/nextsection.gif" border="0" name="bottomnextsection"></a></TD></TR><TR><TD width="100%" colspan="5"></TD><TD width="108" height="1" bgcolor="#000000" align="right"><IMG alt="" height="1" width="108" src="http://www.ibm.com/i/c.gif"></TD></TR><TR><TD background="../i/sw-gold.gif"><a border="0" href="index.html" onMouseOver="iOver('topmain'); iOver('bottommain'); self.status=mainblurb; return true;" onMouseOut="iOut('topmain'); iOut('bottommain'); self.status=''; return true;"><img alt="Main menu" border="0" src="../i/main.gif" name="bottommain"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topsection'); iOver('bottomsection'); self.status=sectionblurb; return true;" onMouseOut="iOut('topsection'); iOut('bottomsection'); self.status=''; return true;" href="index6.html"><img alt="Section menu" border="0" src="../i/section.gif" name="bottomsection"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topfeedback'); iOver('bottomfeedback'); self.status=feedbackblurb; return true;" onMouseOut="iOut('topfeedback'); iOut('bottomfeedback'); self.status=''; return true;" href="j-chat-11-3.html"><img alt="Give feedback on this tutorial" border="0" src="../i/feedback.gif" name="bottomfeedback"></a></TD><TD width="100%" background="../i/sw-gold.gif"><img src="http://www.ibm.com/i/c.gif"></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topprevious'); iOver('bottomprevious'); self.status=previousblurb; return true;" onMouseOut="iOut('topprevious'); iOut('bottomprevious'); self.status=''; return true;" href="j-chat-6-1.html"><img alt="Previous" border="0" src="../i/previous.gif" name="bottomprevious"></a></TD><TD background="../i/sw-gold.gif"><img border="0" src="../i/xnext.gif"></TD></TR><TR><TD width="150" height="1" bgcolor="#000000" colspan="6"><IMG alt="" height="1" width="150" src="http://www.ibm.com/i/c.gif"></TD></TR></TABLE><TABLE cellpadding="0" cellspacing="0" border="0"><TR><TD width="182"><TABLE cellpadding="0" cellspacing="0" border="0" width="182"><TR bgcolor="#000000"><TD align="center" width="60" class="mast"><a style="text-decoration: none; color: #ffffff;" class="nav" href="http://www.ibm.com/privacy/"><font face="Arial, Verdana" size="2">Privacy</font></a></TD><TD width="1" bgcolor="#959595"><img alt="" border="0" height="20" width="1" src="http://www.ibm.com/i/c.gif"></TD><TD align="center" width="60" class="mast"><a style="text-decoration: none; color: #ffffff;" class="nav" href="http://www.ibm.com/legal/"><font face="Arial, Verdana" size="2">Legal</font></a></TD><TD width="1" bgcolor="#959595"><img alt="" border="0" height="20" width="1" src="http://www.ibm.com/i/c.gif"></TD><TD align="center" width="60" class="mast"><a style="text-decoration: none; color: #ffffff;" class="nav" href="http://www.ibm.com/contact/"><font face="Arial, Verdana" size="2">Contact</font></a></TD><TD width="1" bgcolor="#959595"><img alt="" border="0" height="21" width="1" src="http://www.ibm.com/i/c.gif"></TD></TR><TR bgcolor="#ffffff"><TD><img alt="" border="0" height="1" width="1" src="http://www.ibm.com/i/c.gif"></TD></TR></TABLE></TD><TD width="100%"><TABLE cellpadding="0" cellspacing="0" border="0" width="100%"><TR height="21" bgcolor="#000000"><TD><img alt="" border="0" height="21" width="1" src="http://www.ibm.com/i/c.gif"></TD></TR><TR bgcolor="#ffffff"><TD><img alt="" border="0" height="1" width="1" src="http://www.ibm.com/i/c.gif"></TD></TR></TABLE></TD></TR></TABLE></body></html>