This function starts the internal help server, so that HTML help pages are rendered when requested.
startDynamicHelp(start = TRUE)logical: whether to start or shut down the dynamic help
system. If NA, the server is started if not already running.
The chosen port number is returned invisibly (which will be 0
if the server has been stopped).
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 non-zero 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 or options("help.ports")
to 0.
startDynamicHelp is called by functions that need to use the
server, so would rarely be called directly by a user.
Note that options(help_type = "html") must be set to actually
make use of HTML help, although it might be the default for an R
installation.
If the server cannot be started or is disabled,
help.start will be unavailable and requests for HTML
help will give text help (with a warning).
The browser in use does need to be able to connect to the loopback
interface: occasionally it is set to use a proxy for HTTP on all
interfaces, which will not work -- the solution is to add an exception
for 127.0.0.1.
help.start and help(help_type = "html")
will attempt to start the HTTP server if required
Rd2HTML is used to render the package help pages.