SIP .NET is Session Initiation Protocol API for .NET Framework / .NET Core. The API is written in 100% managed C# code.

Features
Digest authentication
Supports TCP and UDP protocols
Supports call hold, call waiting, call transfer, call forward, etc.
Support methods: REGISTER, INVITE, OPTIONS, PRACK, ACK, BYE, CANCEL, MESSAGE, SUBSCRIBE, NOTIFY, UPDATE, INFO, REFER, PUBLISH
Create SDP messages
Parse SDP messages
Register
Unregister

Fuse Angular 7+ version has AoT compiler support out of the box as well as a complete NgRx example app.

MAIN FEATURES
Angular 7+
Angular Material
Google Material Design
BUILT-IN APPLICATIONS
Calendar App
E-Commerce App
Mail App
Mail (NgRx) App
Chat App
File Manager App
Contacts App
Todo App
Scrumboard App

Bitrix24 is a comprehensive free CRM system available both online and as self hosted software that can be installed on your own server. If you go for this option, you’ll get access to open source code as well. Cloud version of Bitrix24 doesn’t have any limits, other than 12 users and 5 GB worth of online storage - you get unlimited leads, contacts, companies, deals, products, quotes, invoices and email marketing. Bitrix24 is also the only free CRM system that comes with integrated call center, so you can make and receive phone calls to/from your CRM as soon are you register.

Anything you do online can be automated with BotChief such as account register, content scraper and article submit etc. It will help you to collect and analyze information, synchronize online accounts, upload and download data, finish any other job that you might do in a web browser, and beyond.