com.freedomotic.helpers.TcpHelper Maven / Gradle / Ivy

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package com.freedomotic.services;

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
 */
public class TcpHelper {

    // Polling delay for socket checks (in milliseconds)
    private static final int POLL_DELAY = 100;

    /**
     * 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
     * @return
     * @throws java.io.InterruptedIOException
     */
    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);
    }

    /**
     * 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
     * @return
     * @throws java.io.InterruptedIOException
     */
    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;
    }

    // Inner class for establishing a socket thread
    // within another thread, to prevent blocking.
    private 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

        SocketThread(String host, int port) {
            // Assign to member variables
            m_host = host;
            m_port = port;
        }
        // Connect to the specified host IP and port number

        SocketThread(InetAddress inetAddr, int port) {
            // Assign to member variables
            m_inet = inetAddr;
            m_port = port;
        }

        @Override
        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() {
            return m_connection != null;
        }

        // Did an error occur?
        public boolean isError() {
            return m_exception != null;
        }
        // Get socket

        public Socket getSocket() {
            return m_connection;
        }
        // Get exception

        public IOException getException() {
            return m_exception;
        }
    }
}