Bandit Level 20 to Level 21

Use netcat to create a client/server connection.

Host name is bandit.labs.overthewire.org 
User: bandit20
password: GbKksEFF4yrVs6il55v6gwY5aVje5f0j

Goal: There is a setuid binary in the homedirectory that does the following: it makes a connection to localhost on the port you specify as a commandline argument. It then reads a line of text from the connection and compares it to the password in the previous level (bandit20). If the password is correct, it will transmit the password for the next level (bandit21).

Commands used for this level:
ls - List information about all the file's
nc -l - arbitrary TCP and UDP connections and listens, when used with -l to specify that nc should listen for an incoming connection rather than initiate a connection to a remote host.
echo - display a line of text

Step 1.
Type ls
We see the suconnect binary file which is described in the goal.

Step 2.
Type ./suconnect
We see we need to run the binary file suconnect with a port number. We also know we need to transmit a password of the current level to login to a open port. To do this we need to create a client/server connection using netcat.
Let's check the netcat man page. 
Type man nc and page down to where it says Client/Server Model. This section gives us everything we need to create a client/server connection. We can test how this works on our own PC by opening two terminal windows. Let's give it a test.
Open two terminal windows on your PC and in the first one type exactly the command that is given under client/server model. Type nc -l 1234 nc is now listening on port 1234 for a connection. Now in the second window we can connect to that open port by typing nc localhost 1234 then go ahead and type something and it will be concatenated to the other terminal window and vice versa. With this test we now see that maybe if we open a listening port in one window and in the other we run our binary file on that open port that maybe we will get our next level password.

Step 3.
Let's start our netcat listening port and echo our current level password to it.
Type echo "GbKksEFF4yrVs6il55v6gwY5aVje5f0j" | nc -l 1234
By doing this we have started a listening port of 1234 (this can be any port # that is not in use) and upon a connection to echo our current password.
Now we need to open a second terminal connection to our level.

Step 4.
Open a second terminal window and connect to the level with: 
Host name is bandit.labs.overthewire.org 
User: bandit20
password: GbKksEFF4yrVs6il55v6gwY5aVje5f0j
Now just like our local test in step 2 we need to run our suconnect binary file to our open listening port of 1234 which is running in our first terminal window.
Type ./suconnect 1234
We get an output of:
Read: GbKksEFF4yrVs6il55v6gwY5aVje5f0j this is our echoed password from the first terminal session we have running netcat in listening mode.
Password matches, sending next password and here we see the password matches and just like noted in the goal our next password is echoed back to our first terminal window. Now go back to our first open terminal window and you will see our next level password is displayed: gE269g2h3mw3pwgrj0Ha9Uoqen1c9DGr

Note: Another way to accomplish this level without opening two windows is to run our first window in the background with the ampersand symbol (&) at the end of our first command like so: echo "GbKksEFF4yrVs6il55v6gwY5aVje5f0j" | nc -l 1234 &
Using the ampersand at the end of a command tells it to be run in the back ground. We could then run our commands for the second terminal in our current terminal while our netcat listening port runs in the background.