Install libpjnath2 by entering the following commands in the terminal:
sudo apt update sudo apt install libpjnath2
PJ Project - NAT handling
PJSIP (a.k.a PJProject) is a multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. It combines signaling protocol (SIP) with rich multimedia framework and NAT traversal functionality into high level API that is portable and suitable for almost any type of systems ranging from desktops, embedded systems, to mobile handsets. . This package includes a NAT handling library.