def l2_recvfrom (client_socket=None, node=None):
"""
This function will be used in Layer 3, the Network layer. Nowhere in this Layer 2
is this function used--rather, this layer purely uses good ol' UDP recvfrom.
"""
while 1:
data = ''.encode()
buffer = ''.encode()
# Read a bunch of bytes up to the MTU or length of data.
while len(data) <= 4096:
buffer, external_address = client_socket.recvfrom(4096-len(data))
if buffer:
data += buffer
else:
#thread.interrupt_main()
break
# This is our protocol. Stop reading when we see \r\n.
if '\r\n'.encode() in buffer:
#thread.interrupt_main()
break
# Split the headers.
packet = data.decode().split('@@')
frame_header = packet[0].split('@')
datagram_header = packet[1].split('@')
# Now we should have something like [Frame, Datagram, Segment].
# Step 1. Build a new Frame.
frame = Frame(frame_header[2], int(frame_header[3]), frame_header[0], int(frame_header[1]),
int(frame_header[4]), packet[1])
# Step 2. Build a new Datagram so we can pass it to l3_recvfrom().
# The order goes 6, 7, then 4, 5 because 6/7 is the destination of this packet, which is
# destined for where the source is. It's backwards since we are receiving, not sending.
datagram = NetworkLayer.Datagram(int(datagram_header[0]), int(datagram_header[1]), int(datagram_header[2]),
int(datagram_header[3]), int(datagram_header[6]), int(datagram_header[7]),
int(datagram_header[4]), int(datagram_header[5]), int(datagram_header[8]),
packet[2])
# l3_recvfrom will return something, but right now, we are not storing that value yet.
#NetworkLayer.l3_recvfrom(datagram)
return len(buffer), frame, datagram, external_address, \
NetworkLayer.l3_recvfrom(client_socket, str(packet[1]+'@@'+packet[2]), node)
def test_communications (self): node = Node.Node(1, 'localhost', 5555) routing_table = RoutingProtocol.DVRP(node) # YOU NEED THE \r\n IN HERE. segment = 'This is a payload.\r\n' node.SetMTU(1500) node.AddLink((1, 'localhost', 1)) # A link to itself... node.AddLink((2, 'localhost', 1)) node.AddLink((3, 'localhost', 1)) client_address, client_socket = LinkLayer.InitializeSocket(node) what_was_sent = NetworkLayer.l3_sendto(client_socket, 2, 5555, routing_table, segment, node) #print(what_was_sent) # Receive it. length_of_buffer, received_frame, datagram_to_pass, external_address, received_segment = \ LinkLayer.l2_recvfrom(client_socket, node) print(received_segment) received_segment.PrintContents()