SIP servlets differ from typical HTTP servlets used in web applications in the following ways:
- HTTP servlets have a particular context (called the context-root) in which they run, while SIP servlets have no context.
- HTTP servlets typically return HTML pages to the requesting client, while SIP servlets typically connect SIP-enabled clients to enable telecommunications between the client and server.
- SIP is a peer-to-peer protocol, unlike HTTP, and SIP servlets can originate SIP requests, unlike HTTP servlets which only send responses to the originating client.
- SIP servlets often act as proxies to other SIP endpoints, while HTTP servlets are typically the final endpoint for incoming HTTP requests.
- SIP servlets can generate multiple responses for a particular request.
- SIP servlets can communicate asynchronously, and are not obligated to respond to incoming requests.
- SIP servlets often work in concert with other SIP servlets to respond to particular SIP requests, unlike HTTP servlets which typically are solely responsible for responding to HTTP requests.