diff --git a/network_monitor.py b/network_monitor.py
index e803f87..4286ba8 100644
--- a/network_monitor.py
+++ b/network_monitor.py
@@ -19,7 +19,29 @@ def log_error(message=None):
         sys.exit(1)
 
 
-def create_usage():
+def get_ifs():
+    """
+    Get a list of network interfaces on the system.
+
+    :rtype : list[str]
+    :return: List of network interfaces.
+    """
+    ifs = []
+    for index, pcapy_device in enumerate(pcapy.findalldevs()):
+        ifs.append(pcapy_device)
+    return ifs
+
+
+def create_usage(ifs):
+    """
+    Return usage string.
+
+    :type ifs: list[str]
+    :param ifs: List of network interfaces to include in help text.
+
+    :rtype : str
+    :return: Usage text.
+    """
     message = """USAGE: network_monitor.py
     <-d|--device DEVICE #>    device to sniff on (see list below)
     [-f|--filter PCAP FILTER] BPF filter string
@@ -27,9 +49,9 @@ def create_usage():
     [-l|--log_level LEVEL]    log level (default 1), increase for more verbosity
     [--port PORT]             TCP port to bind this agent to
 
-Network Device List:"""
-    for index, pcapy_device in enumerate(pcapy.findalldevs()):
-        IFS.append(device)
+Network Device List:
+"""
+    for index, pcapy_device in enumerate(ifs):
         # if we are on windows, try and resolve the device UUID into an IP address.
         if sys.platform.startswith("win"):
             import _winreg
@@ -217,10 +239,10 @@ def set_log_path(self, new_log_path):
         self.log_path = new_log_path
 
 
-if __name__ == "__main__":
-    usage_message = create_usage()
+def main():
+    ifs = get_ifs()
+    usage_message = create_usage(ifs)
     rpc_port = 26001
-    IFS = []
     opts = None
 
     # parse command line options.
@@ -236,7 +258,7 @@ def set_log_path(self, new_log_path):
 
     for opt, arg in opts:
         if opt in ("-d", "--device"):
-            device = IFS[int(arg)]
+            device = ifs[int(arg)]
         if opt in ("-f", "--filter"):
             pcap_filter = arg
         if opt in ("-P", "--log_path"):
@@ -254,3 +276,6 @@ def set_log_path(self, new_log_path):
         servlet.serve_forever()
     except:
         pass
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/setup.py b/setup.py
index 1161a97..b41003f 100644
--- a/setup.py
+++ b/setup.py
@@ -20,5 +20,5 @@
                  'utils': './utils',
                  'web': './web'
                  },
-    install_requires=['pydot2==1.0.33', 'tornado==4.0.2', 'Flask==0.10.1']
+    install_requires=['pydot2==1.0.33', 'tornado==4.0.2', 'Flask==0.10.1', 'pcapy', 'impacket']
 )
\ No newline at end of file