Setting a timeout for socket operations

When I create a socket:

Socket socket = new Socket(ipAddress, port);

It throws an exception, which is OK, because the IP address is not available. (The test variables where String ipAddress = "192.168.0.3" and int port = 300.)

The problem is: how do I set it to timeout for that socket?

When I create the socket, how do I reduce the time before I get a UnknownHostException and get the socket to timeout?

Use the Socket() constructor, and connect(SocketAddress endpoint, int timeout) method instead.

In your case it would look something like:

Socket socket = new Socket();
socket.connect(new InetSocketAddress(ipAddress, port), 1000);

---

Quoting from the documentation

> connect > > public void connect(SocketAddress endpoint, int timeout) throws IOException > > Connects this socket to the server with a specified timeout value. A timeout of zero is interpreted as an infinite timeout. The connection will then block until established or an error occurs. > > Parameters:

> endpoint - the SocketAddress
> timeout - the timeout value to be used in milliseconds. > > Throws: > > IOException - if an error occurs during the connection
> SocketTimeoutException - if timeout expires before connecting
> IllegalBlockingModeException - if this socket has an associated channel, and the channel is in non-blocking mode
> IllegalArgumentException - if endpoint is null or is a SocketAddress subclass not supported by this socket
> > Since: > 1.4

You don't set a timeout for the socket, you set a timeout for the operations you perform on that socket.

For example socket.connect(otherAddress, timeout)

Or socket.setSoTimeout(timeout) for setting a timeout on read() operations.

See: http://docs.oracle.com/javase/7/docs/api/java/net/Socket.html

You could use the following solution:

SocketAddress sockaddr = new InetSocketAddress(ip, port);
// Create your socket
Socket socket = new Socket();
// Connect with 10 s timeout
socket.connect(sockaddr, 10000);

Hope it helps!

Use the default constructor for Socket and then use the connect() method.

You can't control the timeout due to UnknownHostException. These are DNS timings. You can only control the connect timeout given a valid host. None of the preceding answers addresses this point correctly.

But I find it hard to believe that you are really getting an UnknownHostException when you specify an IP address rather than a hostname.

EDIT To control Java's DNS timeouts see this answer.

One solution is to execute the DNS resolution on a different thread which is given only a certain amount of time to complete.

Here's a simple utility that can help you do this:

public class TimeSliceExecutor {

  public static class TimeSliceExecutorException extends RuntimeException {
    public TimeSliceExecutorException(String message, Throwable cause) {
      super(message, cause);
    }
  }

  public static void execute(Runnable runnable, long timeoutInMillis) {
    ExecutorService executor = Executors.newSingleThreadExecutor();
    try {
      Future<?> future = executor.submit(runnable);
      getFuture(future, timeoutInMillis);
    }
    finally {
      if (executor != null) {
        executor.shutdown();
      }
    }
  }

  public static <T> T execute(Callable<T> callable, long timeoutInMillis) {
    ExecutorService executor = Executors.newSingleThreadExecutor();
    try {
      Future<T> future = executor.submit(callable);
      return getFuture(future, timeoutInMillis);
    }
    finally {
      if (executor != null) {
        executor.shutdown();
      }
    }
  }

  public static <T> T getFuture(Future<T> future, long timeoutInMillis) {
    try {
      return future.get(timeoutInMillis, TimeUnit.MILLISECONDS);
    }
    catch (InterruptedException ex) {
      Thread.currentThread().interrupt();
      throw new TimeSliceExecutorException("Interrupton exception", ex);
    }
    catch (ExecutionException ex) {
      throw new TimeSliceExecutorException("Execution exception", ex);
    }
    catch (TimeoutException ex) {
      throw new TimeSliceExecutorException(String.format("%dms timeout reached", timeoutInMillis), ex);
    }
  }
}

Then build the socket along these lines:

private Socket buildSocket() throws IOException {
  final Socket socket = new Socket();
  socket.setSoTimeout(socketTimeout);
  socket.connect(new InetSocketAddress(resolveHost(host, dnsTimeout), port), connectionTimeout);
  return socket;
}

private static InetAddress resolveHost(String host, long dnsTimeout) throws IOException {
  try {
    return TimeSliceExecutor.execute(() -> InetAddress.getByName(host), dnsTimeout);
  }
  catch (TimeSliceExecutor.TimeSliceExecutorException ex) {
    throw new UnknownHostException(host);
  }
}

Ref: https://stackoverflow.com/a/70610305/225217