Silence net::ERR_CONNECTION_REFUSED
Chrome itself is emitting these messages, and there is no way to block them. This is a function of how chrome was built; whenever a ResourceFetcher object attempts to fetch a resource, its response is passed back to its context, and if there's an error, the browser prints it to the console - see here.
Similar question can be found here.
If you'd like, you can use a chrome console filter as this question discusses to block these errors in your console, but there is no way to programmatically block the messages.
I don't know why do you want to prevent this error output. I guess you just want to get rid of them when debugging. So I provide a work around here may be just useful for debugging.
Live demo: http://blackmiaool.com/soa/43012334/boot.html
How to use it?
Open the demo page, click the "boot" button, it will open a new tab. Click the "test" button in the new tab and check the result below. If you want to get a positive result, change the url to wss://echo.websocket.org.
Why?
By using post message, we can make browser tabs communicate with each other. So we can move those error output to a tab that we don't concern.
P.S. You can refresh the target page freely without loosing the connection between it and boot page.
P.P.S You can also use storage event to achieve this.
boot.html:
<!DOCTYPE html><html><head> <meta charset="utf-8" /> <title>boot page</title></head><body> <button onclick="boot()">boot</button> <p>BTW, you can boot the page without the button if you are willing to allow the "pop-up"</p> <script> var targetWindow; function init() { targetWindow } function boot() { targetWindow = window.open("target.html"); } boot(); window.addEventListener('message', function(e) { var msg = e.data; var { action, url, origin, } = msg; if (action === "testUrl") { let ws = new WebSocket(url); ws.addEventListener("error", function() { targetWindow.postMessage({ action: "urlResult", url, data: false, }, origin); ws.close(); }); ws.addEventListener("open", function() { targetWindow.postMessage({ action: "urlResult", url, data: true, }, origin); ws.close(); }); } }); </script></body></html>target.html
<!DOCTYPE html><html><head> <meta charset="utf-8" /> <title>target page</title></head><body> <h4>input the url you want to test:</h4> <textarea type="text" id="input" style="width:300px;height:100px;"> </textarea> <br> <div>try <span style="color:red">wss://echo.websocket.org</span> for success result(may be slow)</div> <button onclick="test()">test</button> <div id="output"></div> <script> var origin = location.origin; var testUrl = origin.replace(/^https?/, "ws") + "/abcdef"; //not available of course document.querySelector("#input").value = testUrl; function output(val) { document.querySelector("#output").textContent = val; } function test() { if (window.opener) { window.opener.postMessage({ action: "testUrl", url: document.querySelector("#input").value, origin, }, origin); } else { alert("opener is not available"); } } window.addEventListener('message', function(e) { var msg = e.data; if (msg.action === "urlResult") { output(`test ${msg.url} result: ${msg.data}`); } }); </script></body></html>