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Update README in yesod-websockets to address the timeout issue.

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Christopher Reichert 2014-12-15 21:58:06 -06:00
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yesod-websockets/README.md
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##README##
## REQUIRED PACKAGES
**REQUIRED PACKAGES:**
chat.hs requires two packages which are not part of yesod-websockets: stm-lifted and conduit-combinators. yesod-websockets can be installed with the command "cabal install". The additional packages can be installed with the command, "cabal install stm-lifted conduit-combinators".
The example, chat.hs, requires `stm-lifted` and `conduit-combinators`
which are not dependencies of `yesod-websockets`. Installing the extra
packages needed for the chat.hs example can be installed with the
command:
**TIMEOUTS:** chat.hs sessions timeout after about 30 seconds of inactivity. One way to control timeouts is to add a few lines of code to chat.hs as follows:
```haskell
getHomeR :: Handler Html
getHomeR = do
webSockets chatApp
defaultLayout $ do
[whamlet|
<div #output>
<form #form>
<input #input autofocus>
|]
toWidget [lucius|
\#output {
width: 600px;
height: 400px;
border: 1px solid black;
margin-bottom: 1em;
p {
margin: 0 0 0.5em 0;
padding: 0 0 0.5em 0;
border-bottom: 1px dashed #99aa99;
}
}
\#input {
width: 600px;
display: block;
}
|]
toWidget [julius|
var url = document.URL,
output = document.getElementById("output"),
form = document.getElementById("form"),
input = document.getElementById("input"),
conn;
$ cabal install stm-lifted conduit-combinators
url = url.replace("http:", "ws:").replace("https:", "wss:");
conn = new WebSocket(url);
conn.onmessage = function(e) {
var p = document.createElement("p");
p.appendChild(document.createTextNode(e.data));
};
/* *******************************************************************************************************
The following code demonstrates one way to prevent timeouts. The "if" test is added to prevent chat participants from getting the ping message “dcba” every twenty seconds. It also prevents participants from receiving any message ending with “dcba” sent by any chat participant. “ e.data.split("").reverse().join("").substring(0,4)” changes, for example, “user:abc123dcba” to “abcd321cba:resu” and grabs the first four characters; i.e., “abcd”. Messages are broadcast only if the last four characters are not “dcba”. Note that the variable "t" controls the length of the timeout period. t = 3 allows one minute of inactivity. t = 30 allows ten minutes, and t = 180 allows an hour. The value inserted below is 360 (2 hours).
START NEW CODE ********************************************************************************* */
## TIMEOUTS
if (e.data.split("").reverse().join("").substring(0,4) != "abcd") {
output.appendChild(p);
}
};
var t = 360
setInterval (function () {
t = t - 1;
if (t > 0)
{
conn.send("dcba");
}
}, 20000);
/* END ******************************************************************************************** */
form.addEventListener("submit", function(e){
conn.send(input.value);
input.value = "";
e.preventDefault();
});
|]
main :: IO ()
```
**NOTE:** A file named "chat-with-timeout-control.hs" is included in this directory. It contains the above code, so unless the variable "t" is changed, it can remain idle for up to two hours before timing out.
Versions of `yesod-websockets` prior to 0.2.1 may experience session
timeouts after about 30 seconds of inactivity. Refer to the patch in
the `websockets` library which addresses this issue:
https://github.com/jaspervdj/websockets/commit/536849d1f3265076f61edefd5c89e84e82a99c71