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import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.InetAddress;
import java.net.Socket;
/**
* This class offers a timeout feature on socket connections.
* A maximum length of time allowed for a connection can be
* specified, along with a host and port.
*
* @author David Reilly (written for JavaWorld)
* @author Daniel Matuschek
* @version $Id: TimedSocket.java,v 1.2 2002/05/31 14:45:56 matuschd Exp $
*
* imported to the net.matuschek.util source tree by Daniel Matuschek
*/
public class TimedSocket
{
/**
* Attempts to connect to a service at the specified address
* and port, for a specified maximum amount of time.
*
* @param addr Address of host
* @param port Port of service
* @param delay Delay in milliseconds
*/
public static Socket getSocket ( InetAddress addr, int port, int delay)
throws InterruptedIOException, IOException
{
// Create a new socket thread, and start it running
SocketThread st = new SocketThread( addr, port );
st.start();
int timer = 0;
Socket sock = null;
for (;;) {
// Check to see if a connection is established
if (st.isConnected()) {
// Yes ... assign to sock variable, and break out of loop
sock = st.getSocket();
break;
} else {
// Check to see if an error occurred
if (st.isError()) {
// No connection could be established
throw (st.getException());
}
try {
// Sleep for a short period of time
Thread.sleep ( POLL_DELAY );
} catch (InterruptedException ie) {}
// Increment timer
timer += POLL_DELAY;
// Check to see if time limit exceeded
if (timer > delay) {
// Can't connect to server
throw new InterruptedIOException("Could not connect for " +
delay + " milliseconds");
}
}
}
return sock;
}
/**
* Attempts to connect to a service at the specified address
* and port, for a specified maximum amount of time.
*
* @param host Hostname of machine
* @param port Port of service
* @param delay Delay in milliseconds
*/
public static Socket getSocket ( String host, int port, int delay)
throws InterruptedIOException, IOException
{
// Convert host into an InetAddress, and call getSocket method
InetAddress inetAddr = InetAddress.getByName (host);
return getSocket ( inetAddr, port, delay );
}
/**
* Inner class for establishing a socket thread
* within another thread, to prevent blocking.
*/
static class SocketThread extends Thread
{
// Socket connection to remote host
volatile private Socket m_connection = null;
// Hostname to connect to
private String m_host = null;
// Internet Address to connect to
private InetAddress m_inet = null;
// Port number to connect to
private int m_port = 0;
// Exception in the event a connection error occurs
private IOException m_exception = null;
// Connect to the specified host and port number
public SocketThread ( String host, int port) {
// Assign to member variables
m_host = host;
m_port = port;
}
// Connect to the specified host IP and port number
public SocketThread ( InetAddress inetAddr, int port ) {
// Assign to member variables
m_inet = inetAddr;
m_port = port;
}
public void run() {
// Socket used for establishing a connection
Socket sock = null;
try {
// Was a string or an inet specified
if (m_host != null) {
// Connect to a remote host - BLOCKING I/O
sock = new Socket (m_host, m_port);
} else {
// Connect to a remote host - BLOCKING I/O
sock = new Socket (m_inet, m_port);
}
}
catch (IOException ioe) {
// Assign to our exception member variable
m_exception = ioe;
return;
}
// If socket constructor returned without error,
// then connection finished
m_connection = sock;
}
// Are we connected?
public boolean isConnected() {
if (m_connection == null)
return false;
else
return true;
}
// Did an error occur?
public boolean isError() {
if (m_exception == null)
return false;
else
return true;
}
// Get socket
public Socket getSocket() {
return m_connection;
}
// Get exception
public IOException getException() {
return m_exception;
}
}
/** Polling delay for socket checks (in milliseconds) */
private static final int POLL_DELAY = 100;
}
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