IP Messenger

IP Messenger is a free and open source very simple to use pop-up-style instant messaging utility which can be used over a LAN (short for Local Area Network) connection.

The IP Messenger utility provides you with secure communication as it uses RSA 2048-bit encryption with the AES (Advanced Encryption Standard) 256-bit encryption algorithm.

Moreover, IP Messenger provides you with fast and high speed file and folder transfers for easy data sharing with your friends and colleagues over a LAN network connection.

Once IP Messenger is installed on your Mac, you can send messages to any of your contacts from the Message menu, selecting the users you want to send it to and clicking the Send button.

When you receive a new message, the message will pop-up and will also display the built-in attachment drawer if you have also been sent a file.

IP Messenger also enables you to enable the Absence mode which allows you to setup an away message that will be automatically sent to anyone trying to contact you.

Here is a contact form for issue report.