Getting Jetty Websocket talking same language as JavaScript Websocket

I wrote a Jetty Websocket Client which is connecting to a remote server and trying to send JSON requests. The server is rejecting the requests as invalid and closing my connection. However, when I send the exact same JSON over using a Javascript client it works just fine. So now I'm left scratching my head is it Jackson 2's encoding of the JSON vs JSON.stringify()? (diff shows the two JSON outputs as exactly the same, no diffs). Is it a different default configuration between Javascript Websockets and Jetty? I'm definitely missing something, bashing my head against the wall.

Java Side Snippet:

final String wsAddress = "ws://" + wssUrl + "/ws";
    final WebSocketClient client = new WebSocketClient();
    final WSEventSocket socket = new WSEventSocket(loginRequest);
    try {
        client.start();

        final ClientUpgradeRequest request = new ClientUpgradeRequest();
        final URI wsUri = new URI(wsAddress);

        logger.info("Connecting to {}", wsUri);
        final Future<Session> session = client.connect(socket, wsUri, request);

        final String requestjson = mapper.writeValueAsString(wsRequestPojo);
        final Future<Void> fut = session.getRemote().sendStringByFuture(requestjson);
...

Javascript side snippet:

var wsRequestJson = {...Use output from Java Side...}
var mySock = new WebSocket("ws://" + wsocketUrl + "/ws");
mySock.onmessage = function(evt) { console.log(evt.data); }; mySock.onclose = function() { console.log("CLOSED"); };
mySock.send(JSON.stringify(wsRequestJson));

The Javascript side works perfectly, the Java side is not encoding the data properly. I've tried abunch of things like JSON to byte array and such no luck. I Wiresharked both transactions and I see the WebSocket pushes and the Responses. In Java I'm seeing a Payload that looks exactly like JSON and Wireshark deciphers it. On the Javascript packets I see some type of encoded data \214P\311n\3020\024... I read a little bit about Masked Payloads and both clients are sending Masked Payloads with Masking-Keys, maybe something to do with that?

Any idea how to get the Java Jetty side to encode the data in a similar fashion? Or even what type of encoding the Javascript side is using? I'm probably over thinking it at this point...

Thanks!

As stated by @Joakim Erdfelt in a comment above the Javascript side is using Sec-Websocket-Extension: permessage-deflate by default. Might not be the best way to set it but I updated my Java code by adding:

request.addExtensions(ExtensionConfig.parse("permessage-deflate"));

Updated Snippet:

final String wsAddress = "ws://" + wssUrl + "/ws";
    final WebSocketClient client = new WebSocketClient();
    final WSEventSocket socket = new WSEventSocket(loginRequest);
    try {
        client.start();

        final ClientUpgradeRequest request = new ClientUpgradeRequest();
        request.addExtensions(ExtensionConfig.parse("permessage-deflate"));
        final URI wsUri = new URI(wsAddress);

        logger.info("Connecting to {}", wsUri);
        final Future<Session> session = client.connect(socket, wsUri, request);

        final String requestjson = mapper.writeValueAsString(wsRequestPojo);
        final Future<Void> fut = session.getRemote().sendStringByFuture(requestjson);
...

Works like a charm! Thanks!