gf -server[=port]

You can now specify which port the HTTP server should run on in server mode.
The default is 41296.

src/compiler/GF/Infra/Option.hs

@@ -74,7 +74,7 @@ errors = fail . unlines
 -- Types
 
 data Mode = ModeVersion | ModeHelp | ModeInteractive | ModeRun | ModeCompiler
-          | ModeServer
+          | ModeServer Int{-port-}
   deriving (Show,Eq,Ord)
 
 data Verbosity = Quiet | Normal | Verbose | Debug
@@ -286,7 +286,8 @@ optDescr =
      Option [] ["batch"] (NoArg (mode ModeCompiler)) "Run in batch compiler mode.",
      Option [] ["interactive"] (NoArg (mode ModeInteractive)) "Run in interactive mode (default).",
      Option [] ["run"] (NoArg (mode ModeRun)) "Run in interactive mode, showing output only (no other messages).",
-     Option [] ["server"] (NoArg (mode ModeServer)) "Run in HTTP server mode.",
+     Option [] ["server"] (OptArg modeServer "port") $
+       "Run in HTTP server mode on given port (default "++show defaultPort++").",
      Option [] ["tags"] (NoArg (set $ \o -> o{optMode = ModeCompiler, optTagsOnly = True})) "Build TAGS file and exit.",
      Option ['E'] [] (NoArg (phase Preproc)) "Stop after preprocessing (with --preproc).",
      Option ['C'] [] (NoArg (phase Convert)) "Stop after conversion to .gf.",
@@ -361,6 +362,12 @@ optDescr =
     ]
  where phase       x = set $ \o -> o { optStopAfterPhase = x }
        mode        x = set $ \o -> o { optMode = x }
+       defaultPort   = 41296
+       modeServer    = maybe (ms defaultPort) readPort
+         where
+           ms = mode . ModeServer
+           readPort p = maybe err ms (readMaybe p)
+                 where err = fail $ "Bad server port: "++p
        verbosity mv  = case mv of
                            Nothing -> set $ \o -> o { optVerbosity = Verbose }
                            Just v  -> case readMaybe v >>= toEnumBounded of