Immediately after accepting a connection, the server issues a single line of text identifying itself. That identification line has the following form:
ODSIMS 0.0 [(vendor_string)]
It is our anticipation that the first ODSIMS protocol specification will not be perfect and will therefore be subject to revisions from time to time. As the ODSIMS specification is modified, the protocol version numbers (PVNs) will increase. Servers implementing revised ODSIMS specifications should replace "0.0" with whatever the well-known version number is for the revised protocol that they implement. This gives clients the opportunity to determine whether they are compatible with their server before attempting to speak the server's language.
It is recommended that all servers implementing a particular protocol version also provide backward support for lower PVNs, because an older client connecting to a newer server will depend on the server's ability to support older protocols. Nevertheless, backward protocol support is an optional feature, so additional steps are necessary to ensure that compatibility can be correctly determined.