Allows to take over transport of message communication initiated by an instrument. Implement this interface to provide a transport of message communication. When an instrument is about to create a server endpoint, it calls the MessageTransport#open(URI, MessageEndpoint) method with the server URI. Usage example:

class RoutedServer implements MessageEndpoint {

    private final MessageEndpoint remoteEndpoint;
    private final OutputStream routerOut = getRouterOutputStream();
    private final WritableByteChannel routerOutChannel;

    RoutedServer(MessageEndpoint remoteEndpoint) {
        this.remoteEndpoint = remoteEndpoint;
        this.routerOutChannel = Channels.newChannel(routerOut);
        new Thread(() -> {
            try {
                runInputLoop();
            } catch (IOException ex) {
            }
        }).start();
    }

    @Override
    public void sendText(String text) throws IOException {
        routerOut.write(text.getBytes());
        routerOut.flush();
    }

    @Override
    public void sendBinary(ByteBuffer data) throws IOException {
        routerOutChannel.write(data);
        routerOut.flush();
    }

    @Override
    public void sendPing(ByteBuffer data) throws IOException {
        remoteEndpoint.sendPong(data);
    }

    @Override
    public void sendPong(ByteBuffer data) throws IOException {
        // Did we send ping?
    }

    @Override
    public void sendClose() throws IOException {
        routerOut.close();
    }

    private void runInputLoop() throws IOException {
        try (InputStream routerIn = getRouterInputStream()) {
            byte[] buf = new byte[1024];
            ByteBuffer bb = ByteBuffer.wrap(buf);
            int l;
            while ((l = routerIn.read(buf)) > 0) {
                bb.limit(l);
                remoteEndpoint.sendBinary(bb);
                bb.rewind();
            }
        } finally {
            remoteEndpoint.sendClose();
        }
    }
}

Engine.newBuilder().serverTransport(
                (uri, peerEndpoint) -> {
                    if (denyHost.equals(uri.getHost())) {
                        throw new MessageTransport.VetoException("Denied access.");
                    } else if (routedURI.equals(uri)) {
                        return new RoutedServer(peerEndpoint);
                    } else {
                        // Permit instruments to setup the servers themselves
                        return null;
                    }
                }).build();