In MTProto, TL constructs will be serialised into binary form before being embedded as the payload of MTProto messages, however we can leave this to the client library which we will be using.Īn example of a TL-Schema (types are declared first, followed by functions with a separator in between): ntCode#efed51d9 phone_registered:Bool phone_code_hash:string send_call_timeout:int is_password:Bool = auth.SentCode ntAppCode#e325edcf phone_registered:Bool phone_code_hash:string send_call_timeout:int is_password:Bool = auth.SentCode -functions- ndCode#768d5f4d phone_number:string sms_type:int api_id:int api_hash:string lang_code:string = auth.SentCode Ī TL function invocation and result using functions and types from the above TL-Schema, and equivalent binary representation (from the official documentation): (ndCode '79991234567' 1 32 'test-hash' 'en') = (ntCode phone_registered:(boolFalse) phone_code_hash:'2dc02d2cda9e615c84' ) d16ff372 3939370b 33323139 37363534 00000001 00000020 73657409 61682d74 00006873 e77e812d = 2215bcbd bc799737 63643212 32643230 39616463 35313665 00343863 e12b7901 TL-Schema layers A TL-Schema is a collection of available types and functions.

Type Language, or TL, is used to represent types and functions used by the API. For example, reading the contents of a conversation involves calling the messages.getMessage function with the necessary parameters and receiving a messages.Messages in return. The Telegram API is RPC-based, so interacting with the API involves sending a payload representing a function invocation and receiving a result. On the other hand, we do need to understand the payload format in order to make API calls.

Fortunately, we don’t need to concern ourselves with it directly when using a client library. It is an application layer protocol which writes directly to an underlying transport stream such as TCP or UDP, and also HTTP. MTProto is the custom encryption scheme which backs Telegram’s promises of security.

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