1. Arguments that act as default for all servers.
2. --http=Spec or --https=Spec is followed by arguments for that server until the next --http=Spec or --https=Spec or the end of the options.
3. If no --http=Spec or --https=Spec appears, one HTTP server is created from the specified parameters.

   Examples:

   --workers=10 --http --https
   --http=8080 --https=8443
   --http=localhost:8080 --workers=1 --https=8443 --workers=25

--port=Port

Start HTTP server at Port. It requires root permission and the option --user=User to open ports below 1000. The default port is 80. If --https is used, the default port is 443.

--ip=IP

Only listen to the given IP address. Typically used as --ip=localhost to restrict access to connections from localhost if the server itself is behind an (Apache) proxy server running on the same host.

--debug=Topic

Enable debugging Topic. See debug/3.

--syslog=Ident

Write debug messages to the syslog daemon using Ident

--user=User

When started as root to open a port below 1000, this option must be provided to switch to the target user for operating the server. The following actions are performed as root, i.e., before switching to User:

• open the socket(s)
• write the pidfile
• setup syslog interaction
• Read the certificate, key and password file (--pwfile=File)

--group=Group

May be used in addition to --user. If omitted, the login group of the target user is used.

--pidfile=File

Write the PID of the daemon process to File.

--output=File

Send output of the process to File. By default, all Prolog console output is discarded.

--fork[=Bool]

If given as --no-fork or --fork=false, the process runs in the foreground.

--http[=(Bool|Port|BindTo:Port)]

Create a plain HTTP server. If the argument is missing or true, create at the specified or default address. Else use the given port and interface. Thus, --http creates a server at port 80, --http=8080 creates one at port 8080 and --http=localhost:8080 creates one at port 8080 that is only accessible from localhost.

--https[=(Bool|Port|BindTo:Port)]

As --http, but creates an HTTPS server. Use --certfile, --keyfile, -pwfile, --password and --cipherlist to configure SSL for this server.

--certfile=File

The server certificate for HTTPS.

--keyfile=File

The server private key for HTTPS.

--pwfile=File

File holding the password for accessing the private key. This is preferred over using --password=PW as it allows using file protection to avoid leaking the password. The file is read before the server drops privileges when started with the --user option.

--password=PW

The password for accessing the private key. See also `--pwfile`.

--cipherlist=Ciphers

One or more cipher strings separated by colons. See the OpenSSL documentation for more information. Starting with SWI-Prolog 7.5.11, the default value is always a set of ciphers that was considered secure enough to prevent all critical attacks at the time of the SWI-Prolog release.

--interactive[=Bool]

If true (default false) implies --no-fork and presents the Prolog toplevel after starting the server.

--gtrace=[Bool]

Use the debugger to trace http_daemon/1.

--sighup=Action

Action to perform on kill -HUP <pid>. Default is reload (running make/0). Alternative is quit, stopping the server.

Other options are converted by argv_options/3 and passed to http_server/1. For example, this allows for:

--workers=Count

Set the number of workers for the multi-threaded server.

http_daemon/0 is defined as below. The start code for a specific server can use this as a starting point, for example for specifying defaults or additional options. This uses guided options processing from argv_options/3 from library(main). The option definitions are available as http_opt_type/3, http_opt_help/2 and http_opt_meta/2

http_daemon :-
    current_prolog_flag(argv, Argv),
    argv_options(Argv, _RestArgv, Options),
    http_daemon(Options).

See also

- http_daemon/1