I have been using/administering GNU/Linux based systems for 15 years and have yet to see where the Bash built-in /dev/tcp was enabled, so any shell script I write that requires sockets I reach for netcat or socat.
$ nc -l 8080 &
[1] 13694
$ echo hi >> /dev/tcp/127.0.0.1/8080
hi
[1]+ Done nc -l 8080
I just tried it on a relatively diverse set of distros. Depending on the version of netcat, if it is an ancient one on an older distribution such as say RHEL4, you have to do:
nc -l -p 8080
However, the same echo command works in all of them.
Btw, the reason why this works even if you dont see anything in /dev/tcp is because when you try to open a socket in bash using /dev/tcp it doesn't talk with the pseudo-filesystem of /dev. Bash actually intercepts the command and issues a connect() to the remote host.