How to make an Echo server with Bash?

How to make an Echo server with Bash?

bash tcp netcat

bash

TCP connection, bash only

linux bash sockets tcp

bash

Using netcat (nc) as an HTTP proxy server and monitor

linux http bash unix tcp

bash

How can I kill TCP port 16969 in Bash?

linux bash ubuntu tcp

bash

Recording messages received on a port with SOCAT

linux bash tcp port socat

bash

Using SSL with Bash's /dev/tcp

bash ssl tcp

bash