The answer to your question would depend on the context in which you're interested.
If you're interested in detecting SPDY servers while browsing the web you'll first need a browser that supports SPDY (e.g. Firefox 11+ or Chrome). In this scenario the best way to detect SPDY is browser dependant.
For Chrome there are a couple of ways:
- You can browse to
chrome://net-internals/#spdy for a list of all currently open SPDY connections (because SPDY connections are persistent - every tab that contains a document from a server which supports SPDY should be present).
- If you're interested only in the current tab you might examine the
window.chrome.loadTimes().wasFetchedViaSpdy DOM property.
For Firefox, the only way I'm aware of is to look for the presence of
X-Firefox-Spdy response header. Do note that for this to work, you must enable SPDY support (it is on by default as of Firefox 13, otherwise - set
All this depends on using a SPDY enabled browser, and manually checking servers. If you'll want to automate this, use a browser that doesn't support SPDY, or just plainly skip the browser - you'll need another strategy. As I see you have two options in this case:
SPDY servers can be configured to advertise their support of SPDY when sending HTTP responses. This would require you to inspect the presence of the appropriate
Alternative-Protocol headers (outlined in the SPDY draft).
Simply establish a TCP connection to the server an send it a SETTIGNS (HELLO) or a SYN_STREAM frame and see if it responds according to the SPDY protocol.