SignalR connect and start cause 404 error

Question

I could not find the specific answer to this when searching so I'm posting my solution here.

We were working fine with SignalR for a long time, then some users started getting 404 errors on the start and connect calls from AngularJs/jQuery to the server. Negotiate would work fine though and return a 200 code.

It turns out by default the server side (ASP.NET 4.6.1) must impose a limit on the size of a URL and instead of returning a 414 (Request-URI Too Long) like you might expect it must just truncate the URL at a length around 2,083 and still try to process it. I'm assuming the 404 is the SignalR hub responding because now the truncated string has query string parameters that don't match what is expected. We were seeing it because we were passing a couple custom values and the security access token via query string parameters which increased the size. The access token was passed via query string because we wanted to use websockets and headers don't exist for websockets. As you add more attributes and roles to your token it will grow which is what put us over the default size limit.

Answer 1

The fix is easy. Just update your server web.config to allow longer URLs.

 <system.web> <httpRuntime targetFramework="4.5" maxRequestLength="30000000" maxUrlLength="40960" maxQueryStringLength="2097151" /> </system.web> <system.webServer> <security> <requestFiltering> <requestLimits maxAllowedContentLength="30000000" maxUrl="40960" maxQueryString="2097151" /> </requestFiltering> </security> </system.webServer>