Seems like a pretty easy challenge as the challenge description says, “Sanity check. crypto.ctf.umbccd.io 13370”. It also gives us a python file: client0.py. On opening the python file we see that the server has 2 methods, and that the flg method will print the flag. 
```Welcome to my sanity check.  You'll find this to be fairly easy.  The oracle is found at umbccd.io:13370, and your methods are:    flg - returns the flag    tst - returns the message after the : in "tst:..."```
Now all we need to do is netcat to crypto.ctf.umbccd.io 13370 & type in ‘flg’ to get our flag! There you go!
Flag: DawgCTF{H3ll0_W0rld!}
View the full writeup [here](https://github.com/abhichitkara/DawgCTF20-Writeups/blob/master/DawgCTF%20Writeups.pdf)