function connect() {
    // 'websocket' -- naming context
    // 'api' -- servlet context
    // 'stomp' -- STOMP endpoint
    var socket = new SockJS('/websocket/api/stomp'); 
    stompClient = Stomp.over(socket);
    stompClient.connect({}, function(frame) {
        stompClient.subscribe('/topic/messages', 
            function(messageOutput) { // JS Object <-- Java OutputMessage
                showMessageOutput(JSON.parse(messageOutput.body)); // JS String --> JS Object
            }
        );
   });
}

function sendMessage() {
    stompClient.send('/channel/chat', 
        {}, // header
	JSON.stringify({...}) // JS Object --> JS String
    );
}