Open Source Kotlin Messaging Platforms

SmsForwarder is an Android application designed to monitor incoming communications such as SMS messages, phone calls, and app notifications, and then automatically forward them to configured destinations based on user-defined rules, making it ideal for remote monitoring, backup, or automation scenarios. Users can set custom logic so that certain messages or notifications trigger forwarding to group chat bots (like DingTalk or enterprise WeChat), webhook endpoints, email, push services (PushPlus, Bark), Telegram bots, and other channels, allowing flexible integration with communication workflows. In addition to basic forwarding, the app’s rule-based engine can filter messages, enabling selective forwarding based on content, sender, or event type, and it can even push details like call logs or device battery status. The tool’s functionality extends to remote control features, which allow a paired server or client to query messages, calls, contacts, and more.

Session Android is the official mobile client for Session, a privacy-first messaging protocol that enables secure, anonymous messaging without requiring phone numbers, email addresses, or centralized user accounts. Built natively for Android, the app lets users send and receive end-to-end encrypted text messages, voice notes, images, and attachments in both one-on-one and group chats, all while routing data through a decentralized onion-routing network designed to protect not just message content but also metadata like sender ID, timing, and network location. The Android client integrates seamlessly with Android’s notification system and background services so that you can stay connected without exposing your identity or compromising privacy, and it supports features such as message reactions, search within chats, profile and contact management, and local message storage encrypted at rest.

Other apps have user IDs: Signal, Matrix, Session, Briar, Jami, Cwtch, etc. SimpleX does not, not even random numbers. This radically improves your privacy. The video shows how you connect to your friend via their 1-time QR-code, in person or via a video link. You can also connect by sharing an invitation link. Temporary anonymous pairwise identifiers SimpleX uses temporary anonymous pairwise addresses and credentials for each user contact or group member. It allows to deliver messages without user profile identifiers, providing better meta-data privacy than alternatives. Many communication platforms are vulnerable to MITM attacks by servers or network providers. To prevent it SimpleX apps pass one-time keys out-of-band when you share an address as a link or a QR code. Double-ratchet protocol. OTR messaging with perfect forward secrecy and break-in recovery. NaCL cryptobox in each queue to prevent traffic correlation between message queues if TLS is compromised.

Element X Android is a modern, reimagined Matrix-protocol client designed for Android that provides secure, decentralized communication with a focus on performance, polished UI, and extensibility. Built as the successor to earlier Matrix clients, Element X blends fast native Android development with a feature-rich experience that supports end-to-end encrypted messaging, voice and video calls, threaded conversations, and file sharing across federated Matrix servers. Unlike proprietary messaging apps, Element X connects to any compliant Matrix server, letting individuals host their own or join communities without centralized control, while still benefiting from robust cryptographic protections that ensure only intended recipients can read conversations. The app’s UI emphasizes responsiveness and ease of use with modern navigation patterns, customizable themes, and intuitive controls for group chats and spaces (Matrix’s equivalent of servers or room collections).

Signal-Android is the official open-source Android client for Signal, a secure messaging app focused on end-to-end encryption and privacy. Developed by the Signal Foundation, it enables private messaging, voice, and video calls, without storing user data. Signal uses the Signal Protocol for encryption and does not collect metadata, making it one of the most privacy-focused communication platforms available.

Element Android is a glossy Matrix collaboration client for Android, based on a new Android SDK fully written in Kotlin. A total rewrite of Riot-Android, Element is an all-in-one secure chat app made possible through the open global Matrix network. It is a messenger that allows users to talk to anyone regardless of their app, while providing unparalleled privacy and security. It protects conversations from data-mining and ads with proper end-to-end encryption, so you can feel totally secure. Element is used by millions all over the world for their business, organizations, and even for personal and home use. It is part of the Matrix ecosystem, which is an open network for secure, decentralised communication governed by The Matrix.org Foundation.

Fall in love with texting all over again with QKSMS! QKSMS is a beautiful, simple and customizable open source replacement to the stock messaging app on Android. It's got a clean, clutter-free intuitive design that lets you focus on what matters, plus millions of colors to choose from to make the theme of the entire app truly your own. QKSMS has some powerful features, including photo sharing, group chat, conversation blocking, message backup and restore and more. It's got everything you need from a text messaging app, plus all the fun features that make for a great text messaging experience. Simply put, QKSMS makes texting magical again, just the way it should be!

This open-source library allows you to integrate Facebook into your Android app. Integrate your Android app with Facebook to build engaging social apps by using the Facebook SDK for Android. To learn more about using Facebook development tools. The current version of the Facebook SDK for Android is version 11.2.0 and requires the Android API 15. Code and samples for the Facebook SDK for Android are available on GitHub. A secure and convenient way for people to log into your app or website by using their Facebook credentials. Enable people to post to Facebook from your app. People can share, send a message, and share to stories. Understand people's actions in your app and measure the effectiveness of your Mobile App Ads. Get data in and out of Facebook's social graph, query data, post stories, upload photos and perform other tasks.

Complete and autonomous NLU solution leveraging opensource libs, such as OpenNLP, Stanford, Duckling and more. Web, mobile, social networks, smart speakers and more. Create your bot once, connect it progressively to multiple channels as you need them. Simple graphical interfaces to build stories and models, manage multilingual and multichannel bots, better understand users with analytics. Program complex stories using Kotlin, Python or Node.js provided components, or integrate with any language by leveraging Tock APIs. Try Tock online, deploy in minutes using Docker running configurations, or setup your own platform to the Cloud, On-Premise, even embedded. More and more teams and companies trust in Tock and open conversational platforms. Built-in connectors for numerous text/voice channels, Messenger, WhatsApp, Google Assistant, Alexa, Twitter and more.

This is based on https://github.com/sys1yagi/mastodon4j The project needs restructuring and updating.