computer networks

The Trivial File Transfer Protocol (TFTP) is an Internet software utility for transferring files that is
simpler to use than the File Transfer Protocol (FTP) but less capable. It is used where user
authentication and directory visibility are not required. For example, it is used by Cisco routers
and switches to transfer images of the operating system from/to the devices.
NOTE: TFTP’s port is 69 (a system/OS port). This is below 1024 and therefore you cannot bind a
Socket to it unless you have administrative access rights on the machine you are working. To
avoid any complications you can use any port > 1024 to bind server sockets.
Task 1: Implementation of the Trivial File Transfer
Protocol (TFTP)
For this task you need to implement (in Java) the Trivial File Transfer Protocol (TFTP) as
specified in RFC 1350 (https://www.ietf.org/rfc/rfc1350.txt) . You will submit source code for a
client and server application that ‘speak’ the TFTP protocol. You will built your protocol on top of
UDP. Compared to the specifications in the RFC, you will implement a slightly simplified version:
Support for octet mode only. The files should be transferred as a raw sequence of bytes. Do
not read, write or transfer files as characters.
Support only for error handling when the server is unable to satisfy the request because the
file cannot be found.
No support for error handling when data duplication occurs.
The client and server applications should be simple Java console applications. The server should
operate (i.e. read and write files) in the directory where it is started from. The server should
support simultaneous file transfers to and from multiple clients. The client should just read
command line arguments (or have a very simple console-based menu – e.g. “press 1 to store file,
press 2 to retrieve file”) and execute user commands (i.e. reading or writing a file).
Hint: the simplest way to implement timeouts is by calling the setSoTimeout() method on the
DatagramSocket objects (assuming that you are using blocking I/O). If the timeout expires, a
java.net.SocketTimeoutException is raised, though the DatagramSocket is still valid.
Task 2: Implementation of an even simpler version of
TFTP on top of TCP
For this task you will use TCP sockets to implement a protocol that operates like TFTP (i.e.
supports only read and write operations). Given that TCP supports in-order, reliable data
transport, you should not implement the relevant mechanisms described in RFC 1350 (ACKs,

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retransmissions). The client and server applications should be equally simple, as in Task 1. The
server must be able to handle multiple file transfers.
Task 3: Interoperability with existing implementations
(5% bonus)
Given that the UDP version of TFTP client and server that you will implement must adhere to the
respective RFC, both the client and server should be able to interoperate with other TFTP servers
and clients, respectively, regardless of the programming language they are written. For this
optional task, you are asked to demonstrate this interoperability by running your client with an
existing third-party server, and your server with an existing third-party client.
Marking Criteria
You should make sure that your code compiles. Code which does not compile will receive at most
20%.
I will assess your assignment using the following criteria:
TFTP-UDP-Server (35%)
Is the server-side of the protocol fully and correctly implemented (based on the specifications
in the RFC)? i.e. read/write requests, acknowledgments, timeouts, error handling, support for
simultaneous file transfers.
TFTP-UDP-Client (30%):
Is the client-side of the protocol fully and correctly implemented (based on the specifications
in the RFC)? i.e. read/write requests, acknowledgments, timeouts, error handling.
TFTP-TCP-Server (10%)
Is the server-side of the protocol fully and correctly implemented? i.e. read/write requests,
error handling, support for simultaneous file transfers.
TFTP-TCP-Client (10%):
Is the client-side of the protocol fully and correctly implemented? i.e. read/write requests,
error handling.
Description of Protocols (10%):
Is there description for both protocols and how/where the specifications are implemented?
Is the description well-written with clear references to the source code?
Other Characteristics (5%):
Is the code commented appropriately?
Is it indented correctly?
Is naming of variables and methods sensible?
Interoperability (extra 5%)

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Is your implementation compatible with third-party TFTP servers and clients and have you
demonstrated that it is?
Note that the maximum mark you can get is 100% and the extra 5% will be added to the mark to
reach up to 100%.

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