`loopback localhost`

IBM® Developer z/OS® and z/OS Debugger use the TCP/IP loopback and TCP/IP localhost definitions. Communication will fail if these definitions are set up using different TCP/IP addresses.

To avoid address resolution issues, define one of the following lines in the local host table, as described in section "Configuring the local host table" of the Communications Server: IP Configuration Guide (SC31-8775).

127.0.0.1 loopback localhost # for IPv4 only
::1 loopback localhost # for IPv6 only

Note: Ensure that the definition is valid for both the MVS and z/OS UNIX search orders.

Refer to Communications Server: IP Configuration Guide (SC31-8775) and Communications Server: IP Configuration Reference (SC31-8776) for additional information on TCP/IP configuration. The IBM Explorer for z/OS Host Reference Guide (SC27-8438) also provides related information in the "Setting up TCP/IP" chapter.