More robust way of picking an unused local port

Fixes #584.

python/ycm/completers/cs/cs_completer.py

@@ -31,12 +31,10 @@ import json
 import subprocess
 import logging
 
-
 SERVER_NOT_FOUND_MSG = ( 'OmniSharp server binary not found at {0}. ' +
 'Did you compile it? You can do so by running ' +
 '"./install.sh --omnisharp-completer".' )
 
-CS_SERVER_PORT_RANGE_START = 10001
 
 class CsharpCompleter( Completer ):
   """
@@ -118,7 +116,7 @@ class CsharpCompleter( Completer ):
     """ Start the OmniSharp server """
     self._logger.info( 'startup' )
 
-    self._omnisharp_port = CS_SERVER_PORT_RANGE_START + os.getpid()
+    self._omnisharp_port = utils.GetUnusedLocalhostPort()
     solutionfiles, folder = _FindSolutionFiles( request_data[ 'filepath' ] )
 
     if len( solutionfiles ) == 0:

python/ycm/utils.py

@@ -22,6 +22,7 @@ import os
 import sys
 import signal
 import functools
+import socket
 
 WIN_PYTHON27_PATH = 'C:\python27\pythonw.exe'
 WIN_PYTHON26_PATH = 'C:\python26\pythonw.exe'
@@ -48,6 +49,15 @@ def PathToTempDir():
   return tempdir
 
 
+def GetUnusedLocalhostPort():
+  sock = socket.socket()
+  # This tells the OS to give us any free port in the range [1024 - 65535]
+  sock.bind( ( '', 0 ) )
+  port = sock.getsockname()[ 1 ]
+  sock.close()
+  return port
+
+
 def PathToPythonInterpreter():
   # This is a bit tricky. Normally, sys.executable has the full path to the
   # Python interpreter. But this code is also executed from inside Vim's

python/ycm/youcompleteme.py

@@ -57,7 +57,7 @@ class YouCompleteMe( object ):
 
 
   def _SetupServer( self ):
-    server_port = SERVER_PORT_RANGE_START + os.getpid()
+    server_port = utils.GetUnusedLocalhostPort()
     with tempfile.NamedTemporaryFile( delete = False ) as options_file:
       self._temp_options_filename = options_file.name
       json.dump( dict( self._user_options ), options_file )