-1 specifies that the PAC port will be set to the autoconfiguration port (the default autoconfiguration port is 8083). This is the default setting.
This variable can be used together with the proxy.config.url_
variable to get a PAC file from a different port. You must create and run a process that serves a PAC file on this port; for example, if you create a Perl script that listens on port 9000 and writes a PAC file in response to any request, you can set this variable to 9000, and browsers that request the PAC file from a proxy server on port 8080 will get the PAC file served by the Perl script.