Configuring Telnet Server on Ubuntu 16.04

======================================

Ubuntu is one of the most popular and widely used Linux distributions for both servers and desktops alike due to its ease of use, robustness, and extensive community support.

In this article, we will cover the steps required to set up a telnet server on an Ubuntu 16.04 system. Telnet itself is a simple network protocol that allows remote access over insecure connections by default (hence why it's not recommended for production environments).

Prerequisites

---------

Before you begin with these instructions:

1. Make sure your Ubuntu machine has the `telnetd` and `xinetd` packages installed.

```bash

sudo apt-get update -y && sudo apt-get install telnetd xinetd -y

```

2. Ensure that networking is enabled on your system.

Step 1: Start Telnet Server Service

-----------------------------

To start the telnet server service, run the following command in a terminal:

```bash

sudo systemctl enable telnet.service

```

If you're using an older version of Ubuntu (16.x), use `service` instead:

```sh

sudo service telinet restart

```

Step 2: Configure Firewall Rules (Optional)

---------------------------------------

To allow incoming traffic on port 23, which is the default Telnet port for both IPv4 and IPv6, you can add a rule to your system's firewall. For example, if you're using `ufw`:

```bash

sudo ufw enable

```

Then, open ports 22 (SSH) and 80/443 (HTTP/HTTPS):

```sh

sudo ufw allow ssh

sudo ufw allow http && sudo ufw allow https

sudo service ufw restart

```

If you're using `iptables` instead:

```bash

ufw --version &>/dev/null || { echo 'You are not running UFW. Please install it first: apt-get update -y; apt-get install firestorm -y'; exit 1; }

# Allow incoming connections from any IP on port 22 (SSH) and ports 80/443 (HTTP/HTTPS)

sudo ufw allow ssh

sudo ufw allow http && sudo ufw allow https

# Apply the changes to your rules. You can also use service iptables restart if you prefer.

service ufw --reload || { echo 'Failed to reload firewallrules'; exit 1; }

```

Step 3: Test Telnet Connection (Optional)

-----------------------------------

Once the above steps are complete, open a new terminal window on another machine in your network and test whether telnet is working by connecting to port 23 of your Ubuntu server:

```bash

telnet :23

```

Troubleshooting Tips:

----------------

* If you encounter any issues while following these instructions or if the telinet service won't start, ensure that networking is enabled on your system and try restarting both `service network` (if using systemd) or `systemctl restart networking`.

```bash

sudo systemctl status network

```

* Also, check whether you've opened port 23 in your firewall rules as described above. You can verify this with the following command:

```sh

sudo ufw --list | grep telnetd

```

-------

In conclusion, setting up a Telinet server on Ubuntu is relatively straightforward and should take no more than five minutes if you follow these instructions carefully. Remember to always secure your system by enabling password authentication for remote logins whenever possible, especially when connecting from untrusted networks.

For further information about configuring telnet servers or securing your Ubuntu installation in general, I recommend consulting the official Ubuntu Server Guide: 'http://www.serverguide.org'(http://serverguide)

Ubuntu 16.04 telnet server