detectclosed.html

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<TITLE>Detecting When a Non-Blocking Socket Is Closed by the Remote Host
(Java Developers Almanac Example)
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  <h3>
    e180.  
    Detecting When a Non-Blocking Socket Is Closed by the Remote Host</h3>

The only way to detect that the remote host has closed the connection
is to attempt to read or write from the connection.  If the remote
host properly closed the connection, <code>read()</code> will return -1.  If
the connection was not terminated normally, <code>read()</code> and
<code>write()</code> will throw an exception.

<P> When using a selector to process events from a non-blocking
socket, the selector will try to return an <code>OP_READ</code> or
<code>OP_WRITE</code> event if the remote host has closed the socket.


<pre>
    try {
        // Read from socket
        int numBytesRead = <font color="#0066ff"><i>socketChannel</i></font>.read(buf);
    
        if (numBytesRead == -1) {
            // No more bytes can be read from the channel
            <font color="#0066ff"><i>socketChannel</i></font>.close();
        } else {
            // Read the bytes from the buffer
        }
    } catch (IOException e) {
        // Connection may have been closed
    }
    
    try {
        // Write to socket
        int numBytesWritten = <font color="#0066ff"><i>socketChannel</i></font>.write(buf);
    } catch (IOException e) {
        // Connection may have been closed
    }
</pre>
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            &nbsp;Related Examples
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e173. <a class="eglink" href="NbClientSocket.html?l=rel">
    Creating a Non-Blocking Socket
</a>
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e174. <a class="eglink" href="ReadSocket.html?l=rel">
    Reading from a SocketChannel
</a>
<br>

e175. <a class="eglink" href="WriteSocket.html?l=rel">
    Writing to a SocketChannel
</a>
<br>

e176. <a class="eglink" href="NbClient.html?l=rel">
    Using a Selector to Manage Non-Blocking Sockets
</a>
<br>

e177. <a class="eglink" href="NbServerSocket.html?l=rel">
    Creating a Non-Blocking Server Socket
</a>
<br>

e178. <a class="eglink" href="AcceptSocket.html?l=rel">
    Accepting a Connection on a ServerSocketChannel
</a>
<br>

e179. <a class="eglink" href="NbServer.html?l=rel">
    Using a Selector to Manage Non-Blocking Server Sockets
</a>
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        See also: 
<a class="eglink" href="/egs/java.nio/pkg.html?l=rel#Byte%20Buffers">
    Byte Buffers
</a>&nbsp;&nbsp;

<a class="eglink" href="/egs/java.nio/pkg.html?l=rel#File%20Locking">
    File Locking
</a>&nbsp;&nbsp;

<a class="eglink" href="/egs/java.nio/pkg.html?l=rel#Files">
    Files
</a>&nbsp;&nbsp;

<a class="eglink" href="/egs/java.nio/pkg.html?l=rel#Streams">
    Streams
</a>&nbsp;&nbsp;

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