While service challenges are often connected to with netcat or PuTTY, solving them will sometimes require using a scripting language like Python. CTF players often use Python alongside pwntools.
netcat is a networking utility found on macOS and linux operating systems and allows for easy connections to CTF challenges. Service challenges will commonly give you an address and a port to connect to. The syntax for connecting to a service challenge with netcat is
nc <ip> <port>.