NonBlockingClient.java

package tlschannel.example;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.StandardCharsets;
import java.security.GeneralSecurityException;
import java.util.Iterator;
import javax.net.ssl.SSLContext;
import tlschannel.ClientTlsChannel;
import tlschannel.NeedsReadException;
import tlschannel.NeedsWriteException;
import tlschannel.TlsChannel;

/** Client non-blocking example. Connects to a public TLS reporting service. */
public class NonBlockingClient {

    public static void main(String[] args) throws IOException, GeneralSecurityException {
        ByteBuffer requestBuffer = ByteBuffer.wrap(SimpleBlockingClient.httpLine.getBytes(StandardCharsets.US_ASCII));
        ByteBuffer responseBuffer = ByteBuffer.allocate(1000); // use small buffer to cause selector loops
        boolean requestSent = false;

        // initialize the SSLContext, a configuration holder, reusable object
        SSLContext sslContext = SSLContext.getDefault();

        Selector selector = Selector.open();

        // connect raw socket channel normally
        try (SocketChannel rawChannel = SocketChannel.open()) {
            rawChannel.configureBlocking(false);
            rawChannel.connect(new InetSocketAddress(SimpleBlockingClient.domain, 443));

            // Note that the raw channel (and not the wrapped one) is registered in the selector
            rawChannel.register(selector, SelectionKey.OP_CONNECT);

            // create TlsChannel builder, combining the raw channel and the SSLEngine, using minimal options
            ClientTlsChannel.Builder builder = ClientTlsChannel.newBuilder(rawChannel, sslContext);

            // instantiate TlsChannel
            try (TlsChannel tlsChannel = builder.build()) {
                mainLoop:
                while (true) {

                    // loop blocks here
                    selector.select();

                    Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                    while (iterator.hasNext()) {
                        SelectionKey key = iterator.next();
                        iterator.remove();
                        if (key.isConnectable()) {
                            if (rawChannel.finishConnect()) {
                                // the channel is registered for writing, because TLS connections are initiated by
                                // clients.
                                rawChannel.register(selector, SelectionKey.OP_WRITE);
                            }
                        } else if (key.isReadable() || key.isWritable()) {
                            try {
                                if (!requestSent) {
                                    // do HTTP request
                                    tlsChannel.write(requestBuffer);
                                    if (requestBuffer.remaining() == 0) {
                                        requestSent = true;
                                    }
                                } else {
                                    // handle HTTP response
                                    int c = tlsChannel.read(responseBuffer);
                                    if (c > 0) {
                                        responseBuffer.flip();
                                        System.out.print(StandardCharsets.UTF_8.decode(responseBuffer));
                                        responseBuffer.compact();
                                    }
                                    if (c < 0) {
                                        tlsChannel.close();
                                        break mainLoop;
                                    }
                                }
                            } catch (NeedsReadException e) {
                                key.interestOps(SelectionKey.OP_READ); // overwrites previous value
                            } catch (NeedsWriteException e) {
                                key.interestOps(SelectionKey.OP_WRITE); // overwrites previous value
                            }
                        } else {
                            throw new IllegalStateException();
                        }
                    }
                }
            }
        }
    }
}