HTTP2C (cleartext) client to HTTP2C server - http2

Question

I have an HTTP2C Embedded Jetty 9.x Server running ... note the server connector shows h2c ...
2016-03-21 09:25:44.082:INFO:oejs.ServerConnector:main: Started ServerConnector#66c7bd3f{HTTP/1.1,[http/1.1, h2c, h2c-17, h2c-16, h2c-15, h2c-14]}{0.0.0.0:8080}
I have an OkHttpClient 3 attempting to talk HTTP2C to this server , however it always gets downgraded to HTTP/1.1, what am I missing? Which Java client API supports HTTP2C? My client code is as below ...
package http2;
import java.util.Collections;
import okhttp3.ConnectionSpec;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
public class GetClear {
public static void main(String[] args) throws Exception {
ConnectionSpec spec = new ConnectionSpec.Builder(ConnectionSpec.CLEARTEXT).build();
OkHttpClient client = new OkHttpClient.Builder().connectionSpecs(Collections.singletonList(spec)).build();
Request request = new Request.Builder().url("http://localhost:8080/test").build();
Response response = client.newCall(request).execute();
System.out.println (response.body().string());
System.out.println("****");
response.body().close();
}
}
[The server prints the 'request.getProtocol' from a Jetty servlet and that shows HTTP/1.1 instead of HTTP/2].
HTTP/2 server and client on TLS works just fine using HTTP/2(client code and server code are different of course).
Any help will be truly appreciated.

Answer 1

Using a Jetty HTTP2C client, the same server code works. I guess OkHTTPClient does not support HTTP2C.

Answer 2

A complete h2c example using the HelloHandler example from the jetty doc:
public class HelloServer {
public static class HelloHandler extends AbstractHandler {
final String greeting;
final String body;
public HelloHandler() {
this("Hello World");
}
public HelloHandler(String greeting) {
this(greeting, null);
}
public HelloHandler(String greeting, String body) {
this.greeting = greeting;
this.body = body;
}
public void handle(String target,
Request baseRequest,
HttpServletRequest request,
HttpServletResponse response) throws IOException,
ServletException {
response.setContentType("text/html; charset=utf-8");
response.setStatus(HttpServletResponse.SC_OK);
PrintWriter out = response.getWriter();
out.println("<h1>" + greeting + "</h1>");
if (body != null) {
out.println(body);
}
baseRequest.setHandled(true);
}
}
public static void main(String[] args) throws Exception {
Server server = new Server();
server.setHandler(new HelloHandler());
HttpConfiguration httpConfig = new HttpConfiguration();
ConnectionFactory h1 = new HttpConnectionFactory(httpConfig);
ConnectionFactory h2c = new HTTP2CServerConnectionFactory(httpConfig);
ServerConnector serverConnector = new ServerConnector(server, h1, h2c);
serverConnector.setPort(8080);
server.setConnectors(new ServerConnector[] { serverConnector });
server.start();
server.join();
}
}

Answer 3

The Jetty log line shows that you have configured the server connector to have HTTP/1.1 to be the default protocol (that is the upper-case "HTTP/1.1" before the brackets containing the list of protocols supported).
You don't show your server-side code, but you have two choices:
Configure explicitly the default protocol for the server connector:
serverConnector.setDefaultProtocol("h2c");
Pass the ConnectionFactory objects in the right order to the server connector, since the first one will be the default protocol:
HttpConfiguration httpConfig = new HttpConfiguration();
ConnectionFactory h1 = new HttpConnectionFactory(httpConfig);
ConnectionFactory h2c = new HTTP2CServerConnectionFactory(httpConfig);
ServerConnector serverConnector = new ServerConnector(server, h2c, h1);