CPSC 3600 - Buffering Large Data Packets

What does this code do?

tcpClient.send(message.encode())

newMessage = tcpClient.recv(2048)

It tells recv to use a 2048 byte recieve buffer

What happens if we need to receive more data than the receive buffer can handle?

Buffer the messages ourselves until all data is received then return to our application

What does this code do?

# Create a message with a header containing the length

message = "I love tigers"*1000message_length = len(message)

data = pack(f"!H{message_length}s", message_length, message.encode()) # "!H13000s"

conn.send(data)

It packs the message length with the message and sends it out

- We send the message length as an unsigned short

Code example : Receiving a message with a length header

Extract the length value from the message

# Begin receiving a new message

data = conn.recv(1024)

fixed_length_header = data[:2] # Array slice: returns the first two elements

length = unpack("!H", fixed_length_header)[0] # unpack returns tuple, we want just # the first element

message = data[2:] # Array slice: return all elements after 2nd

...

Code example : Receiving a mesage with a length header #2

# loop until we've received enough data

while len(message) < length:

length_remaining = length - len(message)

if length_remaining > 1024:

data = conn.recv(1024) # receive more data

message += data # concatenate the data to the rest of the message

else:

data = conn.recv(length_remaining) # receive more data

message += data # concatenate the data to the rest of the message

# once the while loop has exited, we can decode and return the message

return message.decode()

Code example

def get_next_message():

# Protocol: [length of payload, 2 bytes][payload]

# Extract the length value from the message# Begin receiving a new message

data = conn.recv(1024)

length = data[0:2] # Array slice: returns the first two elements

length = unpack("!H", length)[0] # unpack returns tuple, we want first element

payload = data[2:] # Array slice: return all elements after 2nd

# loop until we've received enough data

while len(payload) < length:

length_remaining = length - len(message)

if length_remaining > 1024:

data = conn.recv(1024) # receive more data

message += data # concatenate the data to the rest of the message

else:

data = conn.recv(length_remaining) # receive more data

message += data # concatenate the data to the rest of the message

# once the while loop has exited, we can decode and return the message

return payload.decode()

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