The Word From Abroad

Assigned

Due

Jan 19

45 pts

Jan 31

This is a get-started assignment for using the Cleansocks library. You are to create a simple program which is a client for Quote of the Day protocol, defined in RFC 865. This is testing service, and there's not much too it: When the client connects to a qotd service, the server sends it a short message, then disconnects. Such a server is running on sandbox.mc.edu. The quote service runs on port 17, so, if you have nc installed, you can do this:

[tom@tomslap ~]$ nc sandbox.mc.edu 17 Parents often talk about the younger generation as if they didn't have much of anything to do with it. [tom@tomslap ~]$

This exercise is to build a program using the Cleansocks API which will connect using TCP to port 17 on the indicated server, read the quotation, and print it out, with the small modification of adding two dashes and a space at the front of each line.

[tom@localhost qotd]$ ./qcli5 sandbox.mc.edu -- Some people carve careers, others chisel them. [tom@localhost qotd]$ ./qcli5 sandbox.mc.edu -- If opportunity came disguised as temptation, one knock would be enough. [tom@localhost qotd]$ ./qcli5 sandbox.mc.edu -- Any clod can have the facts, but having opinions is an art. -- -- Charles McCabe [tom@localhost qotd]$ ./qcli5 sandbox.mc.edu -- "There was a boy called Eustace Clarence Scrubb, and he almost deserved it." -- -- C. S. Lewis, "The Chronicles of Narnia" [tom@localhost qotd]$ ./qcli5 sandbox.mc.edu -- Envy, n.: -- Wishing you'd been born with an unfair advantage, -- instead of having to try and acquire one. [tom@localhost qotd]$ ./qcli5 sandbox.mc.edu -- Whitehead's Law: -- The obvious answer is always overlooked. [tom@localhost qotd]$ ./qcli5 sandbox.mc.edu -- George Orwell was an optimist. [tom@localhost qotd]$ ./qcli5 sandbox.mc.edu -- If you are good, you will be assigned all the work. If you are real -- good, you will get out of it.

Some quotes are witty, and there are definitely some of the other kind.

Your program should meet the following requirements:

You must write in C++ and use the provided cleansocks interface.
Take one or two parameters on the command line, the host and the port to connect to. The host is required, and the port is optional. If not specified, use the qotd port number. The computer is specified by name, and the port by name or number.
Connect and print the received message with two dashes and a space added to the front of each line, as shown above.
The default port number (service number) is 17, but do not hard-code the port number. Use lookup_service to get the number for service qotd.
If your program exits due to some error, it should print an appropriate error message. You will need to catch exceptions and print the the contents of the what method to make your messages.
[tom@localhost qotd]$ ./qcli5 server.home Socket operation failed: [connect] No route to host [tom@localhost qotd]$ ./qcli5 bogus.missing.foo Socket operation failed: [IPaddress::lookup(bogus.missing.foo)] Name or service not known [tom@localhost qotd]$ ./qcli5 sandbox.mc.edu broken Bad port number (sandbox.mc.edu)
Don't send any data to the server, but do close the socket after receiving the server's message.

Hints

Feel free to start with one of the posted examples and modify it. (Probably not the server.)
The lookup_service call will accept either the number or the name.
The RFC does not specify how line breaks are coded in the text the server sends you. The server on Sandbox always separates lines with \r\n, but plain \r or plain \n is also possible. make sure your code is flexible.
You may read the data with recv or recvln or a combination, as you see fit.
The posted textbook examples simply die with the uncaught exception when an cleansocks call fails. You should catch the exceptions and print an error message including the text of the what() method from the exception.
Make sure to read from the server in a loop. There is no guarantee that the entire message will arrive in a single recv. You will need to put recv in a loop and read until you reach the end of the message.
Finally, note that data recovered from recv or recvln does not have a plain C string terminator at the end of it, so it is not a legal plain C string. You can either arrange to add a terminator, construct a C++ string using the explicit length, or handle the data as an array instead of a string.
As noted, sandbox runs a qotd service which you may use for testing. Googling “public qotd server” turns up a few others, which should also respond to your client.

Submission

When your program is working, nicely commented and properly indented, submit it using the form here.