We now use a different service endpoint for GET and POST requests.  Upon instantiation of a SOS object, the caller sets the GET URL (as previously), and by default the POST URL is set the same as this GET URL.  Upon fetching the service's capabilities (via the GET URL), the service's POST URL (for XML encoded request/response) is parsed from the DCP section and stored.  This POST URL is then subsequently used for all POST requests.  This allows for different GET/POST endpoints.  Note that this behaviour can be disabled by setting the sos.config.post.setUrlFromCapabilities flag to false.  See this issue for details: https://github.com/52North/sos-js/issues/3.