readme

this gives details of the network programming

tftp testing code. 

The program tftptest acts as a tftp client and does the following:

1. sends a request with a nonsense opcode.

2. sends a RRQ with a filename that does not contain a null

3. starts a file transfer (needs the file named medium to be available) and 
sends an invalid message where the server is expecting an ACK.

Expected results:

for test 1, the server should either send an error message or ignore.
If the server crashes this is bad.

test 2: same as 1, just trying to crash the server

test 3: server should send back first data message and the second. Once it
is sent the bad ACK it can send back an error or ignore. The server should 
continue to send the last DATA messge ACKED, but the client is not longer 
around to read it - in this case the server must time out after re-sending
some number of times (this may take up to a minute to happen).


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Testing with tftp.

1. verify that the files small, medium and large can all be transferred
accurately.

set the tftp options "trace" and "verbose" before the remaining tests,
this allows you to see what the client is doing, and also slows things
down enough that you can interrupt a transfer.

2. start transfer of the file large and suspend the client in the middle
of a transfer (press ^C). The server should timeout waiting for the ACKs.
There should be some retransmissions, but eventually the server must give up
or this is bad. I"ve suggested values like 5 seconds per timeout and waiting no
more than 5 retransmissions, so this may take 25 seconds to happen (or more).


3. start transfer of the file large and suspend the client in the middle
of a transfer (press ^Z). The server should timeout waiting for the ACK and
retransmit. now type "fg" to bring resume the tftp client program, the server
must now pick up where it left off and complete the file transfer. Make sure
the file received by the client is correct!

4. start tansfer of the large file on 2 clients at the same time (to
test server concurrency).  Make sure both the clients are actually
transferring at the same time. You probably need to run the clients in
different directories, or receive to different file names, or the
output file will be corrupt...

===============

Grading:

Test 1 (polite clients) is worth a total of 30 points. 10 for each file.

Test 4 (polite concurrent clients) is worth 15 points.

Tests 2 and 3 are part of "server works properly when datagrams are
lost". test 2 is worth 5 points and test 3 is worth 10 points.

the tftpclient program sends garbage in an attempt to crash the
server. I would suggest doing this last. This is worth 15 points, 5
points for each of the 3 tests described above. The file "expected"
contains sample correct output, but you need to keep in mind that some
people may have the server send back a TFTP error message so it is
possible this will show up in the output of testclient.  It is fine if
an error message is received by the client!