Websocket Programming

Ark1st 2019. 9. 27. 14:37

2019. 9. 27. 14:37

1. How to run Java scripts in a web browser

In the Chrome browser, Ctrl + Shift + I to access developer tools. You can run JavaScript directly from the Console tab.

2. Java script to open a web connection

1) Source

<!DOCTYPE html>
<meta charset="utf-8" />
<title>WebSocket Test</title>
<script language="javascript" type="text/javascript">

    var wsUri = "ws://echo.websocket.org/";
var output;
var loopCount = 0;

function init()
{
  output = document.getElementById("output");
  testWebSocket();
}
function testWebSocket()
{
  websocket = new WebSocket(wsUri);
  websocket.onopen = function(evt) { onOpen(evt) };
  websocket.onclose = function(evt) { onClose(evt) };
  websocket.onmessage = function(evt) { onMessage(evt) };
  websocket.onerror = function(evt) { onError(evt) };
}

function onOpen(evt)
  {
    writeToScreen("CONNECTED");
	doSend("Hello "+loopCount.toString());

  } 
function onClose(evt)
  {
    writeToScreen("DISCONNECTED");
  }

  function onMessage(evt)
  {
    writeToScreen('<span style="color: blue;">RESPONSE: ' + evt.data+'</span>');
	if (loopCount < 10)
	{
		doSend("Hello "+loopCount.toString());
		loopCount = loopCount + 1;
	}
	else
	{
	    websocket.close();
	}

  }

  function onError(evt)
  {
    writeToScreen('<span style="color: red;">ERROR:</span> ' + evt.data);
  }

  function doSend(message)
  {
    writeToScreen("SENT: " + message);
    websocket.send(message);
  }

  function writeToScreen(message)
  {
    var pre = document.createElement("p");
    pre.style.wordWrap = "break-word";
    pre.innerHTML = message;
    output.appendChild(pre);
  }
  window.addEventListener("load", init, false);
  </script>
  <h2>WebSocket Test</h2>
  <div id="output"></div>