Peers can start discovery at ~ the same time

Still needs some improvement, hard to test because socket has to be bound.

Shared/Disc0very.py

@@ -1,13 +1,15 @@
 from socket import *
 from random import getrandbits
+from random import choice
 from time import time
 from time import sleep
 import Utils
 import Logging
 from _thread import start_new_thread
 
+
 HEY = "HEY".encode()
-IDENT_SEED_LENGTH = 64
+NAY = "NAY".encode()
 WHAT = "WHAT".encode()
 
 
@@ -17,34 +19,40 @@ class MissingInterfaceError(TypeError):
 
 
 class Disc0very:
-	def __init__(self, port, interface="eth0", max_peers=32):
+	def __init__(self, port, interface=None, max_peers=32):
 		self.port = port
-		self.ident = getrandbits(max_peers * 2)
 		self.sock = socket(AF_INET, SOCK_DGRAM)
 		self.sock.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
 		self.sock.setsockopt(SOL_SOCKET, SO_BROADCAST, 1)
 		self.sock.bind(("", self.port))
+		self.ip_address = Utils.get_ip_address(interface)
 		self.discovering = False
 		self.enlisting = False
 		
 
 
-
+	# Not thread-safe if ran in parallel with __enlist
-	def discover(self, time_out=2):
+	def discover(self, time_out=1):
-		if not self.enlisting:
-			self.discovering = True
 		self.sock.setblocking(False)
-			self.sock.sendto(HEY, ('255.255.255.255', self.port))
 		end_time = time() + time_out
 		servers = []
+		self.sock.sendto(HEY, ('255.255.255.255', self.port))
 		while time() < end_time:
 			try:
-					data = self.sock.recv(512)
+				data, address = self.sock.recvfrom(512)
-					if data != HEY:
+				address = address[0]
+				# If enlisted peer responds with ip address
+				if data not in (HEY, NAY) and address != self.ip_address and not data in servers:
 					servers.append(data)
+				# If another peer is currently discovering
+				elif data == HEY and address != self.ip_address:
+					self.sock.sendto(NAY, ('255.255.255.255', self.port))
+					return self.discover(time_out=time_out)
+				# If another peer gave up
+				elif data == NAY and address != self.ip_address:
+					return None
 			except BlockingIOError:
-					sleep(0.2)
+				sleep((choice(range(1, 10)) / 2) / 10)
-			self.discovering = False
 		if len(servers) == 0:
 			return None
 		elif len(servers) > 1:
@@ -54,43 +62,36 @@ class Disc0very:
 		
 
 	def enlist(self, interface, blocking=False):
-		if not self.discovering:
 		if blocking:
 			self.__enlist(interface)
 		else:
 			start_new_thread(self.__enlist, (interface, ))
 
 
+	# Not thread-safe if ran in parallel with discover
 	# Interface should always be provided when using a Wallaby
 	# because wlan0 and wlan1 have an IP address assigned
 	def __enlist(self, interface=None):
-		self.enlisting = True
 		self.sock.setblocking(True)
-		ip_address = Utils.get_ip_address(interface)
 		data = ""
 		while True:
 			try:
-				data = self.sock.recv(512)
+				data, address = self.sock.recvfrom(512)
 			except BlockingIOError:
 				sleep(0.1)
 			if data == HEY:
-				self.sock.sendto(ip_address.encode(), ('255.255.255.255', self.port))
+				self.sock.sendto(self.ip_address.encode(), ('255.255.255.255', self.port))
 			elif data == WHAT:
 				Logging.error("Apparently more than one server is running. "
 					"Investigating...")
 			 	# Discover and if other server is found shutdown
 
 
-def start():
-	print("starting")
-
-
 if __name__ == "__main__":
-	from time import sleep
 	disc0very = Disc0very(3077)
 	server = disc0very.discover()
 	if not server:
-		print("enlisted")
+		print("enlisting")
 		disc0very.enlist(None, blocking=True)
 	else:
 		print(server)