PL/I programmers should note that (although the segments exchanged between the Listener and implicit-mode servers resemble IMS™ segments) the segments are actually sent by TCP/IP socket calls and do not necessarily follow the standard IMS convention for the PL/I language interface. Specifically, the length field in a segment (TRM or RSM), which is passed via a TCP/IP socket call, must be a halfword (FIXED BIN(15)) and not a fullword.