There are no standard defined framing characters or protocol expressed (including but not limited to SOAP, http, tcp/ip, SFTP, FTPS, etc).
Trading partners decide – I think HIPAA requires some level of secure connection.
There are replies. That again is up to the Trading Partners but typically with this Transaction set there is a TA1 which is an evaluation of the envelope and general structure of the 270 and can be a 997 which does a more indepth evaluation of the content. The 271 itself can contain ERR segments to indicate further issues at the application level.
The supplier of the 270 and the receiver of the 271 should provide User Guides which will tell you how the respective trading partners are utilizing the standard.
Some do not provide the whole particulars for the envelope (ISA/IEA, GS/GE, and sometimes ST/SE).
Inside Cloverleaf the ‘Envelope’ needs to be stripped off then placed back at delivery. There are Cloverleaf provided procs to do this.
Inside your Xlate you may need to get at some of the envelope particulars – there are no provided procs for that but I have some.
There is probably more but the above is from old recollections but should geet you started.
email: jim.kosloskey@jim-kosloskey.com 29+ years Cloverleaf, 59 years IT - old fart.