Lab 3A

Create a TCP Echo Server that mimmicks and sends back all of the data received from the client.

You will be using struct.pack() to simulate a binary protocol.

Lab 3B.1

Pack the values (1, 2, -3, -4) as the following data types (unsigned short, unsigned int, signed short, signed int)

1 as an unsigned short

2 as an unsigned int

-3 as a signed short

-4 as a signed int

Write a TCP client that packs those values, sends the packed string to a server.

Write a TCP server that receives the string, unpacks it using little endian and prints it, then unpacks it again using big endian and prints it.

Lab 3B.2

Create a TCP client. Pack the following values using network byte order: 12345, 56789, &, *, 0x7d0, 0b11111010000. Send the packed string to the TCP echo server. Have the server unpack the values and send them back to the client. Also try encode()/decode() modules and compare different types of encoding.

Q1) Which unpacked are the same?

Q2) Why are they the same? Does it matter what Endianess your system is using?

Q3) Assume I repeat this lab with a client on a little-endian architecture, and the server on a big-endian architecture. How will the files change? Why?

Q4) How can I be sure that the data I send is properly received on any endian machine?

Lab 3C

Write a UDP receiver that receives a string, and orders the words from longest to shortest in a new string.

That new string should be sent to the remote port+1.

(i.e. the source port of message from the SENDER's POV)

Write a UDP sender that sends the initial string, and receives the response from the receiver above (you can use multiple receivers or combine them).

Hint: The second step is intentionally ambiguous on how to proceed. There are multiple solutions.

host to network byte order

buffer sizes

socket timeout

Router Solicitation, Neighbor Solicitation, and Redirect message