CSE333 Exercise 14

• Practice with TCP and client-side networking.

Write a C++ program that accepts three command-line arguments in the following order:

• the hostname of a server
• the port number of that server
• the name of a local file

The program should connect (via TCP) to the server on the supplied hostname and port. Once connected, the program should read the bytes from the local file, and it should write those bytes over the TCP connection. Once all of the bytes have been written, the program should close the TCP connection and exit.

To get you started on this, we have provided you with the following four files. To download the files, go to the link here. The first two are already implemented for you and the last two are skeleton files:

• Makefile: compiles the code into an executable called ex14.
• SocketUtil.h: declares various utility functions to achieve the functionality described above.
• SocketUtil.cc: contains empty implementations of the utility functions declared in the header file.
• ex14.cc: contains an empty main function.

To execute the application, you should type in something like:

$ ./ex14 localhost 5555 test.txt

Note: the values of your command line arguments may vary depending on how you setup your testing.

Implementation Notes

Code Adaption: Feel free to adapt sample code from lecture and section as part of your solution if it helps, but be sure you understand what your code does when you're done.

User Input: Since you will be reading in user input via command line arguements, you should make sure your code handles various inputs from the user, which may be in an unexpected format. Note that the three inputs you get from the user in this exercise each has a different expected format.

Read/Write: You should use POSIX read() to read in the local file and POSIX write() to write over the socket to the server.

Error Handling & Robustness: When you are using POSIX functions, you should make sure that you handle possible errors correctly by retrying in the case of recoverable errors (EAGAIN and EINTR) and returning appropriate status in the case of a non-recoverable error. If you encounter a fatal error in main, you can simply exit the program gracefully. Be sure to clean up resources accordingly in all cases.

Testing Notes

Server Setup: To test your program, you will need to set up a server to receive the data your ex14 executable will send. One way to do this is using the nc program. For example:

$ nc -l 5555 > output.bytes

will run a netcat listener on port 5555 and redirect the incoming bytes to the file output.bytes (i.e., write if it didn’t exist, overwrite if it does exist).

Local Testing: If you are running the server on the same computer/host that you are testing your code on, you can use the special loop-back IP address 127.0.0.1 or localhost to refer to the same host. Please note that each attu (e.g., attu1, attu2) counts as its own host, so if you are running on attu you can only reliably use 127.0.0.1 or localhost if both client and server are running on the same one. And as a reminder, you can choose to log into a specific attu machine by doing

$ ssh <your_netid>@attu#.cs.washington.edu

where # should be replaced by a number between 1 to 8.

Restarting: Note that nc will exit once it has processed a single connection, so you'll need to rerun nc each time you test your client.

Don’t forget that good practices from previous exercises still apply!

General: For the sake of our autograder, you may not modify SocketUtil.h, which also means that you should not modify the function signatures in SocketUtil.cc.

C vs. C++ Idioms: To work with the POSIX networking API, we, unfortunately, have to mix C and C++ idioms in our code. But you should still try to use C++ idioms when possible (e.g., use cout instead of printf, use C++ casting, etc.).

Files to submit:

• SocketUtil.cc
• ex14.cc

Your code must:

• Compile without errors or warnings on CSE Linux machines (lab workstations, attu, or CSE home VM)
• Have no runtime errors, memory leaks, or memory errors
• Be contained in the four files described above. Our provided Makefile should compile your code without errors or warnings.
• Have a comment at the top of your SocketUtil.cc, ex14.cc with your name, student number, and CSE or UW email address. These are the only two files you need to submit for this exercise.
• Be pretty: the formatting, modularization, variable and function names, commenting, and so on should make us smile rather than cry. Additionally, the linter (cpplint.py) shouldn’t have any complaints about your code.
• Be robust: your code should deal with hard-to-handle/edge cases and bogus user input (if there are any) gracefully.

Submit your code on Gradescope