How would you troubleshoot the "Connection refused" error when trying to set up a TCP chat server using Ruby on Ubuntu (WSL)?

Question

I want to create a TCP chat server using Ruby. When I attempt to do this in the Ubuntu terminal (WSL), I encounter the following problem: when I execute the command telnet localhost 2000, I get the following output: Trying ::1... Trying 127.0.0.1... Trying 127.0.0.1... telnet: Unable to connect to remote host: Connection refused enter image description here

Ruby Code :

require 'socket'


server = TCPServer.new(2000) # Server bound to port 2000

while true 
    connection = server.accept   # Wait for a client to connect

    connect.print" Enter ur Username: "
    name = connection.gets.chomp # chomps removes the new line character
    connection.puts "Welcome #{name} to the chat room"
    connection.close             # Disconnect from the client


end 

What I Tried: I attempted to create a TCP chat server using Ruby in the Ubuntu terminal (WSL).

What I Expected to Happen: I expected the server to successfully start and listen on the specified port (in this case, port 2000). When I used the telnet localhost 2000 command, I anticipated a successful connection to the server.

What Actually Resulted: Instead, the telnet command output showed the following: Trying ::1... Trying 127.0.0.1... Trying 127.0.0.1... telnet: Unable to connect to remote host: Connection refused

Answer 1

If the host is returning connection refused, that is because there is no process listening on the server at that port.

In this case, since you are on the localhost -> run netstat from that system and see if you can confirm it is listening.

Pls. keep keep in mind, this the error displayed is from a specific network interaction. In some cases, something "in-between" (like a local software firewall or system config), could also intercept the TELNET connection, and decide to reject the connection even if there is a process happily listening on the port you requested.