A timeout feature on socket connections
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 */publicclass 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 */publicstatic 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 thrownew 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 */publicstatic 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. */staticclass SocketThread extends Thread { // Socket connection to remote host volatileprivate 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 privateint 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; } publicvoid 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? publicboolean isConnected() { if (m_connection == null) return false; elsereturn true; } // Did an error occur? publicboolean isError() { if (m_exception == null) return false; elsereturn true; } // Get socket public Socket getSocket() { return m_connection; } // Get exception public IOException getException() { return m_exception; } } /** Polling delay for socket checks (in milliseconds) */privatestaticfinalint POLL_DELAY = 100; } Related examples in the same category
