Allow --port range for random port selection

.gitignore

@@ -1,2 +1,5 @@
 *.pyc
 *.swp
+build
+dist
+horde.egg-info

README.md

@@ -72,3 +72,4 @@ much more bueno.  One would simply need to:
 * [Nate House](https://github.com/naterh)
 * [Russ Garrett](http://github.com/russss)
 * [Laurie Denness](http://github.com/lozzd)
+* [Sam Gleske](https://github.com/samrocketman)

horde/horde.py

@@ -1,15 +1,15 @@
 #!/usr/bin/env python
+import argparse
 import logging
 import os
+import random
 import re
 import socket
 import subprocess
 import sys
 import tempfile
 import threading
 import time
-
-import argparse
 import BitTornado.BT1.track as bttrack
 import BitTornado.BT1.makemetafile as makemetafile
 import murder_client as murder_client
@@ -31,6 +31,68 @@
 horde_py = os.path.join(horde_root, 'horde.py')
 
 
+def get_random_open_port(port, interface=""):
+    """
+        Arguments:
+            port - can be a single number or a number range with a hyphen as a string
+            interface - a string representing either a hostname in Internet domain notation or IP
+                address to test binding.  By default a blank value means test a binding for all
+                interfaces.
+        Returns:
+            returns an int between 1 and 65535 based on input port
+
+        If a single port is given as input then it simply returns the port
+
+        If a port range is input then a random port will be returned if there is no
+        Listening socket for that port.
+    """
+    regex=re.compile(r'[0-9]+-{0,1}[0-9]*')
+    #if port is an integer then convert to string
+    if isinstance(port, int):
+        port = str(port)
+    #Do some error checking on the input.
+    if not isinstance(port, str):
+        raise TypeError("port not of type str.")
+    if not regex.match(port):
+        raise ValueError("port str must be a number or a range of numbers between 1 and 65535.")
+    ports = sorted(map(lambda x: int(x), port.split('-')))
+    #Do range checking on the input.
+    if len(ports) == 2 and ( ports[1] > 65535 ):
+        raise ValueError("port range is between 1 and 65535.")
+    elif ports[0] < 1 or ports[0] > 65535:
+        raise ValueError("port range is between 1 and 65535.")
+    #Return a port or a random range.
+    if len(ports) == 1:
+        #Since we're given a single port don't even try to test it.  Just return the value.
+        return ports[0]
+    else:
+        port = random.randrange(ports[0],ports[1]+1)
+        count = 0
+        found = False
+        while not found:
+            try:
+                #test the socket for a listening service
+                s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+                #The SO_REUSEADDR flag tells the kernel to reuse a local socket in TIME_WAIT
+                #state, without waiting for its natural timeout to expire.  This avoids
+                #an exception "OSError: [Errno 98] Address already in use" because we are
+                #only testing the binding of a socket and not using it for communication.
+                s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+                s.bind((interface, port))
+                found = True
+            except socket.error,e:
+                #Generate another port to be tested because the last one had a listening socket.
+                port = random.randrange(ports[0], ports[1]+1)
+            s.close()
+            count += 1
+            #avoid an infinite loop
+            if count > 10000:
+                break
+        if not found:
+            raise socket.error("could not obtain socket from port or port range.")
+        return port
+
+
 def run(local_file, remote_file, hosts):
     start = time.time()
     log.info("Spawning tracker...")
@@ -144,7 +206,8 @@ def mktorrent(file_name, tracker):
 
 
 def track():
-    bttrack.track(["--dfile", opts['data_file'], "--port", opts['port']])
+    bttrack.track(["--dfile", opts['data_file'], "--port",
+                    opts['port']])
 
 
 def seed(torrent, local_file):
@@ -187,7 +250,7 @@ def run_with_opts(local_file, remote_file, hosts='', retry=0, port=8998,
     opts['remote-file'] = remote_file
     opts['hosts'] = hosts
     opts['retry'] = retry
-    opts['port'] = port
+    opts['port'] = get_random_open_port(port)
     opts['remote_path'] = remote_path
     opts['data_file'] = data_file
     opts['log_dir'] = log_dir
@@ -217,7 +280,8 @@ def entry_point():
 
     parser.add_argument('--port',
                         default=8998,
-                        help="Port number to run the tracker on")
+                        help="Port number to run the tracker on. Port range " +
+                        "for random port selection also allowed (e.g. 8000-9000).")
 
     parser.add_argument('--remote-path',
                         default='/tmp/horde',
@@ -241,6 +305,9 @@ def entry_point():
 
     opts = vars(parser.parse_args())
 
+    #potentially select a random port
+    opts['port'] = get_random_open_port(opts['port'])
+
     if opts['seed']:
         seed(opts['local-file'], opts['remote-file'])
     else: