To send data over a network, the data has to conform to a certain format or protocol. The Transmission Control Protocol (TCP/IP) is one of the core protocols to be used on the Internet. The following screenshot shows how to communicate over TCP/IP between a Julia Tcp server and a client (see the code in Chapter 8\tcpserver.jl):

The server (in the upper-left corner) is started in a Julia session with server = listen(8080) that returns a TcpServer object listening on the port 8080. The line conn = accept(server) waits for an incoming client to make a connection. Now, in a second terminal (in the lower-right corner), start the netcat (nc) tool at the prompt to make a connection with the Julia server on port 8080, for example, nc localhost 8080. Then, the accept function creates a TcpSocket object on which the server can read or write.

Then, the server issues the command line = readline(conn), blocking the server until it gets a full line (ending with a newline...