When using an SSL enabled credential the P4_PORT variable contains the correct host and port but does not display the SSL prefix so it cannot be used. For example:

But in the job when we display P4_PORT:

[SSL_Freestyle] $ /bin/sh -xe /tmp/jenkins9008466315547409153.sh
+ echo P4_PORT is 10.1.3.163:1866
P4_PORT is 10.1.3.163:1866
+ echo P4_CLIENT is jenkins-master-SSL_Freestyle-1
P4_CLIENT is jenkins-master-SSL_Freestyle-1
Finished: SUCCESS

Reproduction steps:

(1) Setup an SSL enabled P4D server.

(2) Create a credential for the SSL server in Jenkins.

(3) Create a freestyle job that uses the credential. Add a build step that displays P4_PORT. For example on Linux:

echo P4PORT is $P4_PORT

(4) Run the job.