An basic TCP echo server and client.

## SERVER
$ clang main.cxx
$ ./a.out server

# Server listening on port 5000
NOTE: Now start the client in another terminal
# Client connected: 127.0.0.1:49763
# Received message: Hello, World! (13 bytes)
# Sent echo: Hello, World! (13 bytes)

## CLIENT
$ ./a.out client

# Sent message: Hello, World! (13 bytes)
# Received echo: Hello, World! (13 bytes)