added tcp comms to dspctl (#160)

* added tcp comms to dspctl

dpsctl/dpsctl.py

@@ -151,6 +151,55 @@ def read(self):
         return bytes_
 
 
+class tcp_interface(comm_interface):
+    """
+    A class that describes a TCP interface
+    """
+
+    _socket = None
+
+    def __init__(self, if_name):
+        super(tcp_interface, self).__init__(if_name)
+
+        self._if_name = if_name
+
+    def open(self):
+        try:
+            self._socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+            self._socket.settimeout(1.0)
+            self._socket.connect((self._if_name, 5005))
+        except socket.error:
+            return False
+        return True
+
+    def close(self):
+        self._socket.close()
+        self._socket = None
+        return True
+
+    def write(self, bytes_):
+        try:
+            self._socket.send(bytes_)
+        except socket.error as msg:
+            fail("{} ({:d})".format(str(msg[0]), msg[1]))
+        return True
+
+    def read(self):
+        bytes_ = bytearray()
+        sof = False
+        while True:
+            b = self._socket.recv(1)
+            b = ord(b)
+            if b == uframe._SOF:
+                bytes_ = bytearray()
+                sof = True
+            if sof:
+                bytes_.append(b)
+            if b == uframe._EOF:
+                break
+        return bytes_
+
+
 class udp_interface(comm_interface):
     """
     A class that describes a UDP interface
@@ -652,6 +701,8 @@ def create_comms(args):
     if if_name is not None:
         if is_ip_address(if_name):
             comms = udp_interface(if_name)
+        elif if_name[0:4] == "tcp:":
+            comms = tcp_interface(if_name[4:])
         else:
             comms = tty_interface(if_name, args.baudrate)
     else:
@@ -1114,7 +1165,7 @@ def main():
     testing = '--testing' in sys.argv
     parser = argparse.ArgumentParser(description='Instrument an OpenDPS device')
 
-    parser.add_argument('-d', '--device', help="OpenDPS device to connect to. Can be a /dev/tty device or an IP number. If omitted, dpsctl.py will try the environment variable DPSIF", default='')
+    parser.add_argument('-d', '--device', help="OpenDPS device to connect to. Can be a /dev/tty device, IP address for UDP protocol or tcp:IP for TCP protocol. If omitted, dpsctl.py will try the environment variable DPSIF", default='')
     parser.add_argument('-b', '--baudrate', type=int, dest="baudrate", help="Set baudrate used for serial communications", default=9600)
     parser.add_argument('-B', '--brightness', type=int, help="Set display brightness (0..100)")
     parser.add_argument('-S', '--scan', action="store_true", help="Scan for OpenDPS wifi devices")