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When is it preferable to use ws.terminate() VS ws.close()

I know terminate hard closes a socket not letting it hang or send more packets like close does, and terminate sends a different code when closing a socket (1006 vs close sending 1000). So this raises the question, why would I even used ws.close() when I dont plan on reopening a socket? Ive seen so many examples that just use ws.close() and never reopen it. Is it just not well known or standard or is there something behind the scenes Im not aware of?

Closing the web socket will wait for buffered messages to be finished, and initiate the closing handshake. This includes an optional close code and an optional close reason. It tells client that the websocket is now closed and no further messages will be sent, and once the other end acknowledges that, the tcp connection will be closed. See 1.4 Closing handshake:
The closing handshake is intended to complement the TCP closing handshake (FIN/ACK), on the basis that the TCP closing handshake is not always reliable end-to-end, especially in the presence of intercepting proxies and other intermediaries.
By sending a Close frame and waiting for a Close frame in response, certain cases are avoided where data may be unnecessarily lost. For instance, on some platforms, if a socket is closed with data in the receive queue, a RST packet is sent, which will then cause recv() to fail for the party that received the RST, even if there was data waiting to be read.
This is considered a clean closure. The close code informs the status on the other end, or leads to status 1005 if omitted.
Terminating the web socket will just drop the connection. It calls socket.destroy(), no close frames are sent or anything, not even the tcp connection is closed cleanly with FIN. This leads to status 1006 on the other end, after it has run into a timeout.
The downside of having a closing handshake in the protocol is that a closing connection might be left hanging in a limbo state when the other end is no longer responding at all. Only a timeout will end that, with various problems.
Why would I even use ws.close() when I don't plan on reopening a socket?
You should always gracefully close() your web socket to notify the other end that the connection ends. You should also send the close reason 1000 (as the client) or 1001 (as the server) to tell the other end that they should not try to reconnect.
If a server needs to drop the connection but will become available again soon after, it might forcibly close the TCP connection. This will cause the client to immediately detect an abnormal closure, and it might attempt to automatically reconnect after a short time. (There is no method to do this in the ws library, you'd have to call ws._socket.end()).
If you terminate() a working connection, the other end will not notice anything. Only when it tries to send something (e.g. a ping()), after some timeout it will find that the tcp connection was lost and the websocket will become abnormally closed. Don't do that!
You should only ever call terminate() if you have determined that the connection has already been lost - like in the heartbeat example. This will free up resources on your end quickly and immediately fire the respective stream events on the ws object.

WebSockets not closing on IE if closing handshake is never made

I've been implementing a WebSocket with JavaScript and I have this one problem:
The endpoint that my web-application is connected to doesn't send back a close control frame when I'm sending it one.
This isn't that bad because browsers close the WebSocket connection after a while.
But a few things to notice are:
Browsers do only allow a specific amount of WebSockets to be connected at the same time.
When refreshing the web-application a new WebSocket is created
This causes the problem on IE:
When refreshing the web-application more than 6 times, a WebSocket connection cannot be made.
It seems like IE doesn't "delete" the WebSockets if they haven't been closed cleanly. And what's odd is that the amount of web sockets never seems to decrease by refreshing or just by waiting.
Only by closing the browser window, or the tab resets the number of WebSockets to 0.
I've done some researching and this is what I've found out:
Browsers do only support a specific amount of WebSockets to be connected at the same time.
IE supports 6 websockets to be connected [link]
Chrome supports 255 websockets to be connected [link].
And socket.onclose() isn't triggered when you do socket.close(), it is called when the endpoint responses with a close message. [link]
IE waits 15 seconds for the endpoint to send the close message [link].
Chrome waits for 60s for the responding message [Sorry, no link for this, found this out by testing].
If no response message is received, the browser closes the WebSocket connection and a TimeoutError should occur.
Please correct me if I'm wrong :)
I've tried to use unbeforeload to disconnect from the endpoint in hope that the browser would close the connection after a while, but with no luck. [link].
It can also be the cause of that IE aren't able to do request inside the unbeforeload function [link].
Question:
Is there any way to reset the number of WebSockets that are
connected in the browser to the endpoint with JavaScript?
Is there a way to disconnect a WebSocket from the endpoint immediately without closing the connection cleanly?
Is the only way to get this to work to inform the ones who host their endpoint make some changes so they do send a closing frame back?
Is there anything I've misunderstood or that I could try to get this to work?
Here is (in my opinion) good documentation about the WebSocket protocols if somebody would like to read more about it [link1] [link2].
UPDATE:
Only by refreshing the web-application on IE the WebSockets don't get destroyed.
If you navigate between pages in the web-application a new WebSocket will be made but the last WebSocket will get destroyed.

If it is just an edge case problem, then using a http fallback might be your only option. I guess you already do this for proxy servers that block socket connection away.

There is just 1 idea to verify (unconfirmed). Unfortunately, don't have access to IE to verify.
Application may open websocket connection in WebWorker/iFrame. During page refresh, "websocket connection scope" will be deleted, and connection is freed
EXPLANATION
This content from the question body:
Only by refreshing the web-application on IE the WebSockets don't get destroyed. If you navigate between pages in the web-application a new WebSocket will be made but the last WebSocket will get destroyed.
Says that Websocket connection is not destroyed ONLY when page refreshes. During normal navigation, everything is OK.
So, if websocket connection is opened within other scope which will be deleted during page reload, then hopefully connection will be destroyed.

Socket.io: disconnect, reconnect events etc

I am trying to get a handle on the various connection/disconnection events and how to use these to make sure that my application will always terminate gracefully.
I understand that socket.io will automatically attempt to reconnect a specified number of times. It is my understanding that as the connection goes down and subsequently reconnects there will be a disconnection event fired server side. I do not care about the connection temporarily going down so long as it comes back up at some point.
However if there is a more permanent disconnect, I do care about this and would need to update data such as connected users. I understand that on the client side you can get a reconnect_failed error object but I do not believe you can listen for this on the server. Is there any way to get notification on the server side that the connection is down and reconnection has failed? If so how does socket.io implement this?
I could issue a timeout upon a disconnection event server side that removes users if there is no reconnection. I could also have the server ping all connected clients at certain intervals. Are these kinds of solutions the only way to completely deal with all kinds of possible disconnections?

node.js - how to get disconnect event with socket.io? [duplicate]

I have a client/server application using nodejs on the server and socket.io as the connection mechanism. For reasons relevant to my application I want to have only one active connection per browser, and reject all the connections from other tabs that may be opened later on during the session. This works great with WebSockets, but if WebSockets is not supported by the browser and XHR-polling is used instead, the disconnection never happens, so if the user just refreshes the page, this is not interpreted as a reconnection ( I have a delay for reconnection and session restoring), but as a new tab, which ends in the connection being rejected because the old connection made by this same tab is still active.
I'm looking for a way to effectively end the connection from the client whenever a refresh occurs. I've tried binding to the beforeunload and calling socket.disconnect() on the client side, and also sending a message like socket.emit('force-disconnect') and triggering the disconnect from the server with no success. Am I missing something here? Appreciate your help!
I've read this question and couldn't find it useful for my particular case.

Solved the issue, it turns out it was a bug introduced in socket.io 0.9.5. If you have this issue just update BOTH your server and client-side code to socket.io > 0.9.9 and set the socket.io client-side options sync disconnect on unload to true and you're all set.
Options are set this way:
var socket = io.connect('http://yourdomain.com', {'sync disconnect on unload' : true});

You can also get "Error: xhr poll error" if you run out of open file descriptors available. This is likely to happen during a load test.
Check the current open file descriptor size:
ulimit -n
Increase it to a high number:
ulimit -n 1000000

Socket.io events not firing once connected after previous failed attempt

Here's the scenario, I have a client side application, served by PHP on a different server to the node.js + socket.io application. It can connect and receive broadcasts sent from the server. If the connection drops, the application falls back to polling a database (using setInterval()). It attempts to reconnect every 5 polls, and it can successfully reconnect and continue to receive messages.
My problem occurs when the user loads the page and the node server cannot be reached (I turned it off for testing), I then turn on the server and on the 5th poll, it successfully connects to the server, using socket.socket.reconnect();. However, whenever the server broadcasts messages, it doesn't fire the event. Note that this doesn't happen when testing on a phone (which falls back to a different socket method)
I have already seen the question found here Reconnection in socket.io problem in `socket.on('message',function(){})`, however, the socket has not previously been connected so I don't think it could be the session?
EDIT: I changed the socket.socket.reconnect() to socket.socket.connect() and it fixed the problem. If someone could explain the reasons of why this works I'd like to know. I know its because the server isn't actually reconnecting, but would like more info.
Thanks.

well you possibly know the reason for this. server is not reconnecting. it is actually connecting. when you tell socket.io to reconnect it searches for the previous connection handle and thats where the problem arises.