How to receive messages in group chats using telegram bot api

Question

My telegram bot receives messages sent by user to my bot in private chats but not receives messages sent by users in group chats. Any options/api for getting group chat mess

Answer 1

You can access all avaliable settings from all of your bots by sending /mybots to Botfather. Choose the bot, then Bot Settings and Group Privacy. If its disable (default), you can tap on Turn off.

Now its possible to receive the chat history using GetUpdates. This can be done via HTTP API or the frameworks. For example, in C# (.NET Core) like this:

var bot = new TelegramBotClient(ApiToken);
var updates = bot.GetUpdatesAsync().Result;
foreach(var update in updates) {
    Console.WriteLine($"{update.ChannelPost.Date} {update.ChannelPost.Text}");
}

But keep in mind that this feature has some kind of perfect forward secrecy implemented. So you only get messages that were send after group privacy is disabled. As a result, the GetUpdates result is empty until some post was made.