The TCP/IP started task must be active for you to use ISPF Client/Server.
The TSO/ISPF userid must be authorized to use z/OS® UNIX services. Failure to obtain proper authorization will result in message ISPPO22 when an ISPF Client/Server connection is attempted. The "network data" portion of this message will show a TCP/IP socket error code of 156 (EMVSINITIAL).
Authorization status for basic z/OS UNIX services can be determined by entering the OMVS command from the TSO READY prompt. This example indicates that the TSO user is not authorized to use z/OS UNIX services:
READY
omvs
FSUM2057I No session was started. This TSO/E user ID does not have
access to OpenMVS.+
READY
It is not necessary to run the z/OS UNIX shell to use the z/OS UNIX socket implementation with ISPF.