Telegram-iOS/docs/superpowers/specs/2026-04-09-reflector-support-design.md

tgcalls CLI: UDP Reflector Mode

Overview

Add a --mode reflector option to the tgcalls CLI test tool, routing both call instances through a real Telegram UDP reflector instead of direct P2P loopback.

CLI Interface

• --mode p2p — current behavior (direct P2P loopback, no servers)
• --mode reflector — route through a real Telegram UDP reflector
• --mode is required. Exit with usage error if missing.
• --reflector host:port — specifies the reflector address. Required when --mode reflector. Error if missing in reflector mode or if provided with --mode p2p.
• --duration and --quiet are unchanged.

Reflector Configuration

When --mode reflector:

Peer Tag Generation

Generate 16 random bytes. Copy to make two tags:

• Caller tag: byte 0 = 0x00
• Callee tag: byte 0 = 0x01

RtcServer Setup

Each instance gets one RtcServer entry with its respective peer tag:

Field	Value
id	1
host	from --reflector argument
port	from --reflector argument
login	"reflector"
password	hex-encoded 16-byte peer tag (differs by side)
isTurn	true
isTcp	false

Descriptor Changes

• config.enableP2P = false
• rtcServers populated with the single reflector server
• No customParameters changes (standalone reflector mode is not used)

P2P Mode

Unchanged from current behavior: enableP2P = true, empty rtcServers.

Summary Output

Add a mode line to the call summary:

Mode:              reflector (91.108.13.2:596)

or:

Mode:              p2p

No other output changes. The existing audio validation (440Hz sine, non-silence detection) remains the success criterion for both modes.