｢‍｣ Lingenic

HSV Streaming v1.0

Framing, flow control, and device switching

HSV Streaming defines how to send HSV over connections: WebSocket, TCP, serial. Framing with STX/ETX, flow control with XON/XOFF, chunked transfers with ETB/EM, device switching with DC2/DC4. Conforms to RFC 20.

Message Types

Three forms:

[SOH] [header] [STX] [content] [ETX]    Header + content
[STX] [content] [ETX]                   Content only
[SOH] [header] [STX] [ETX]              Header only (empty content)

SOH starts a header. STX terminates the header and starts content. ETX ends the block.

This matches the original ASCII design: SOH begins routing/control info, STX marks where content begins, ETX marks the end.

Content Blocks

STX/ETX frames content. Any payload format works:

# Plain text
[STX] Hello World [ETX]

# JSON
[STX] {"user": "alice", "action": "login"} [ETX]

# HSV records
[STX] name [US] Alice [RS] age [US] 30 [ETX]

# XML
[STX] <message>Hello</message> [ETX]

# Raw binary (DLE transparency)
[STX] [DLE] [STX] <raw PNG bytes> [DLE] [ETX] [ETX]

# Multi-line content (newlines are literal)
[STX] Line one
Line two
Line three [ETX]

# Code with special characters (no escaping needed)
[STX] if (x < 10 && y > 5) { return "yes"; } [ETX]

# Unicode, emoji, RTL, CJK (all valid)
[STX] Hello 世界! Привет мир! مرحبا 🎉🚀✨ [ETX]

# Math and symbols
[STX] ∀x ∈ ℝ: x² ≥ 0 ∧ √(x²) = |x| [ETX]

# Mixed scripts
[STX] English · Ελληνικά · עברית · 日本語 · 한국어 [ETX]

Any data format inside. Seven control characters pass through as literal data:

These can be used for terminal animation or any application needing whitespace/formatting.

Headers

SOH starts a header, STX ends it:

[SOH] hsv [US] 1.0 [RS] type [US] request [STX] [content] [ETX]    Header + content
[SOH] route [US] chat [RS] user [US] alice [STX] [content] [ETX]   Routing + content
[SOH] ack [US] msg-123 [STX] [ETX]                                 Header only (control message)

Headers use HSV structure ([US] for key-value, [RS] for properties). Applications define their own header schemas.

Session

Server sends header on connect:

[SOH] hsv [US] 1.0 [RS] protocol [US] stream [STX] [ETX]

End session:

␄

Flow Control

␓ (0x13)    XOFF - pause output
␑ (0x11)    XON - resume output
␖ (0x16)    Sync/keepalive
␆            Acknowledged
␕            Error/resend
␘            Cancel operation

Chunked Transfer

␗ (0x17)    End of block, more coming
␙ (0x19)    End of medium, data exhausted

␗ for streaming large data. ␙ signals "no more data" (distinct from ␄ which ends the session).

Backend Switching

Device Control characters for distributed architecture:

␒ (0x12)    Connect to backend
␔ (0x14)    Disconnect (return to lobby)

Example:

␒ chat [ETX]     Connect to chat service
␔                Return to lobby

Enables edge + backend architecture where a lobby handles auth/routing and backends are private HSV servers.

Reserved vs Allowed vs Forbidden

Why Forbidden?

NUL (0x00) — C string terminator. Functions like strlen(), strcpy(), and most string APIs stop at NUL. Data gets silently truncated. Database fields, log entries, filenames — anything touching C code risks corruption. Even "safe" languages often use C libraries underneath.

SUB (0x1A) — Ctrl+Z, the DOS/Windows end-of-file marker. Open a file in text mode on Windows, and reading stops at 0x1A. Streams get truncated mid-transfer. Copy a file with SUB in it, get half a file. This isn't legacy — it's still the default behavior in 2026.

ESC (0x1B) — The escape character that starts terminal control sequences. An attacker who can inject ESC into your stream can: change terminal colors, move the cursor, clear the screen, redefine keys, and in some terminals execute arbitrary commands. Decades of CVEs. HSV forbids ESC entirely — if you need terminal control, use HSV's structured operations instead.

If your data contains these bytes, use binary mode (DLE transparency).

Comparison

vs JSON Streaming (NDJSON)

{"msg":"line 1\nline 2"}
{"code":"if (x < 3 \u0026\u0026 y > 5)"}
{"html":"\u003cdiv\u003eHello\u003c/div\u003e"}

[STX] {"msg":"line 1
line 2"} [ETX]
[STX] {"code":"if (x < 3 && y > 5)"} [ETX]
[STX] {"html":"
Hello
"} [ETX]

NDJSON requires escaping newlines, and JSON requires escaping <, >, & in strings. HSV frames the JSON—content passes through unchanged.

vs Length-Prefixed

0x00 0x00 0x00 0x0C Hello World!

Must buffer entire message to know length.
Can't stream partial content.
Binary header not human-readable.

[STX] Hello World! [ETX]

Stream bytes as they arrive.
Send ␗ for partial chunks.
Inspect with any text tool.

vs WebSocket

Message framing only.
No routing metadata standard.
No acknowledgment protocol.
No backpressure signaling.
No chunked transfer.

[SOH] route [US] chat [STX] Hello! [ETX]
Routing in header, content in body.
␆ acknowledge, ␕ request resend.
␓ pause, ␑ resume.
␗ partial, ␙ complete.

WebSocket provides reliable transport. HSV adds application-level semantics: routing, acknowledgment, flow control, chunking.

Multi-format Example

[SOH] type [US] json [STX] {"x":1} [ETX]
[SOH] type [US] xml [STX] <x>1</x> [ETX]
[SOH] type [US] text [STX] Hello 🌍 [ETX]
[SOH] type [US] hsv [STX] x [US] 1 [ETX]

Framing is consistent
Payload format varies
Routing via headers
No escaping anywhere

HSV Streaming adds framing to any payload format. Content can contain newlines, quotes, emoji, any bytes except the 22 reserved.

Transport

Example: Chat Protocol

# Connect (header only)
[SOH] hsv [US] 1.0 [RS] protocol [US] chat [RS] user [US] alice [STX] [ETX]

# Send message (content only)
[STX] Hello everyone! [ETX]

# Receive message (header + content)
[SOH] from [US] bob [STX] Hi Alice! [ETX]

# Acknowledge
␆

# Disconnect
␄

Simple request/response, pub/sub, or bidirectional — HSV Streaming provides the framing and flow control.