Question

Well, the title is quite self-explanatory… Is it possible to set default port number for R’s HTML help? Each time I start HTML help, port number gets changed.

Answer 1

From help(startDynamicHelp):

Details:

 This function starts the internal HTTP server, which runs on the
 loopback interface (‘127.0.0.1’).  If ‘options("help.ports")’ is
 set to a vector of integer values, ‘startDynamicHelp’ will try
 those ports in order; otherwise, it tries up to 10 random ports to
 find one not in use.  It can be disabled by setting the
 environment variable ‘R_DISABLE_HTTPD’ to a non-empty value.

So it looks like you can try to override it via options("help.ports"), appropriately set. The randomization appears to be a feature.