The message "DID NOT RECEIVE FULL CFB HEADER; SOCKET CLOSED" is produced when we receive buffer (the header part of CFBDATA) from TCPIP and do not get the entire number of bytes of data. It could be that the data transmission is slow and we give up before all of the bytes arrive or the packets get lost. All that the Listener knows is it did not get the complete number of bytes after it tried a number of times and so produces the message and Closes the socket. (It does not continue processing where it then checks the length of the CFB to determine if it is >32k.)
Possible changes to address this are increasing the REATIME on the EZACONFG entry for TISN listener or set the values in the TIRSLTMX parms REATOUTS and REATOUTM.