| Internet-Draft | SOLEC | March 2026 |
| bt | Expires 30 September 2026 | [Page] |
This document describes working principles, features and network protocol of SOLEC system.¶
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SOLEC is currently under development for PWR group project and as part of my engineering thesis.¶
System of Lightweight Electronic Communication or SOLEC is a system for decentralised communication designed for low-speed networks. It uses binary protocol to keep required bandwidth as low as possible.¶
Current implementation works on top of TCP/IP stack. In future, SOLEC will be adapted to work over LoRa.¶
Recurring problem with modern day instant messaging is its centralisation. SOLEC solves is it in similar fashion to XMPP or SMTP. SOLEC servers exchange messages between each other so the users using server A can reach out users using server B.¶
User can exchange messages with other users of the network if they are both in their contacts group. Messages from untrusted users are not forwarded by the server. If users are using different servers chat history is stored on both.¶
In current version session is provided by TCP connection. Security of client-server connection can be achieved using TLS.¶
SOLEC is using Type Length Value (TLV) structure for data exchange.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Payload ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
Figure: SOLEC PDU Layout¶
Type (8): Payload type is indicated by 1 octet which gives 256 types that can be represented.¶
Length (16): Payload length is 2 octets. It indicates length of the payload field. The length does not include type and length fields.¶
Payload (variable): Payload stores set of fields determined by its type.¶
Payload usually consist of one or more data fields but it is possible for payload to be empty. Some payload types are used only to signal some event and does not carry any data.¶
Data types are basic types that are used in construction of more complex payload types.¶
Numeric types are Big-Endian. Numeric types names are taken from Go language spec. Following types are in use:¶
Uint64 containing Unix timestamp in UTC timezone.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Timestamp | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
String is prefixed with two octets indicating number of bytes that it occupies. Text is encoded using UTF-8.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | UTF-8 string ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
Figure: String Layout¶
Payload type attributes describes following characteristics:¶
| Type | Name | Attributes |
|---|---|---|
| 0x00 | R | |
| 0x01 | Success | SCE |
| 0x02 | Error | S |
| 0x03 | Handshake | SC |
| 0x04 | Auth | C |
| 0x05 | Message | SC |
| 0xFF | Test | R |
0 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ | Error Type | +-+-+-+-+-+-+-+-+¶
| Type | Description |
|---|---|
| 0x01 | Auth failed. Invalid username or password. |
0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ver_major | ver_minor | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | username (string) ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | password (string) ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | source_address (string) ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | target_address (string) ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | timestamp | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | message_content (string) ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
Test payload is used for encoder and decoders testing. Clients and servers should ignore this kind of payload.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | num1 (uint8) | time1 (timestamp) | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| | | str1 (string) ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | num2 (uint16) | str2 (string) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | num3 (uint32) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | str3 (string) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | num4 (uint64) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
Some operations require multiple rounds of communication. In this case payloads are send in a sequence. Payload that is not part of this specific operation (for example incoming message) cannot interrupt this process.¶