Dayon!

An easy-to-use, cross-platform remote desktop support solution for everyone
It can be used as free alternative to various commercial remote desktop and remote assistance products.

Its key features are

• no router or network configuration required on the assisted side
• very low bandwidth usage
• friendly, multilingual (de/en/es/fr/it/ru/tr/zh) user interface
• assistant and assisted functionality in one packet
• secure, encrypted communication (TLS)
• free and open source