To aid in portability, DSOM has been written to use a common communications interface, which is implemented by one or more available local protocols.
The common communications interface is represented as an abstract class, called Sockets, and is based on the familiar "sockets" interface. Several protocol implementations are supported as Sockets subclasses: TCPIPSockets (and TCPIPSockets32 for OS/2) for TCP/IP, the class NBSockets for Netbios, and the class IPXSockets for Netware IPX/SPX. (The libraries included in a particular SOMobjects run-time package will vary.)
There is one case where a Sockets subclass is not required: the DSOM Workstation run-time package uses shared memory to pass messages within a single machine, and bypasses the use of a Sockets subclass. (The SOMSOCKETS environment variable is ignored.)
When the Event Management Framework (EMan) is used with DSOM, a Sockets subclass will be needed to support EMan, whether or not the application runs completely within a single machine.
Appendix C, "Implementing Sockets Subclasses," describes how an application might provide its own Sockets subclass implementation, for special circumstances.