Interoperability Guide

One of DDS's greatest strengths is interoperability. HDDS can communicate with other DDS implementations out of the box, thanks to the standardized RTPS wire protocol.

Verified Interoperability (9/9 Scenarios)

HDDS has been tested and verified to interoperate with all major DDS implementations:

Implementation	Version	Direction	Samples	Status
FastDDS	3.1.x	FastDDS → HDDS	583	✅
FastDDS	3.1.x	HDDS → FastDDS	435/448 (97%)	✅
RTI Connext	6.1.0	RTI → HDDS	57	✅
RTI Connext	6.1.0	HDDS → RTI	90/90 (100%)	✅
RTI Connext	7.3.0	RTI → HDDS	49/50 (98%)	✅
CycloneDDS	0.10.x	Cyclone → HDDS	50/50	✅
CycloneDDS	0.10.x	HDDS → Cyclone	50/50	✅
OpenDDS	3.28.x	OpenDDS → HDDS	20/20 (100%)	✅
HDDS	latest	HDDS → HDDS	50/50	✅

RTPS Protocol Versions

Implementation	RTPS Version	Vendor ID
HDDS	2.3 (*)	0x01aa
FastDDS	2.3	0x010f
RTI Connext 6.x	2.3	0x0101
RTI Connext 7.x	2.5	0x0101
CycloneDDS	2.3	0x0110
OpenDDS	2.3	0x0103

RTPS version numbers

(*) The "RTPS Version" column shows the wire protocol version advertised in RTPS headers. HDDS advertises 2.3 for maximum compatibility but implements the full RTPS 2.5 specification (as shown in the README badge). RTI Connext 7.3.0 advertises 2.5, which HDDS handles automatically.

Key Features Validated

Feature	Tests	Status
SPDP Discovery	9/9 vendors	✅
SEDP Discovery	9/9 vendors	✅
Reliable communication	All scenarios	✅
Best-Effort communication	All scenarios	✅
XCDR1 serialization	FastDDS, RTI, Cyclone	✅
XCDR2 serialization	All vendors	✅
Multi-node cluster	Cross-machine	✅
96 QoS policy combinations	Validator suite	✅

How Interoperability Works

All compliant DDS implementations use the RTPS (Real-Time Publish Subscribe) protocol for communication. This means:

1. Automatic Discovery - Participants find each other via SPDP multicast
2. Wire Compatibility - Data is serialized using CDR2 format
3. QoS Negotiation - Compatible QoS policies are matched automatically

Quick Start

To communicate between HDDS and another DDS implementation:

1. Use the same Domain ID (e.g., domain 0)
2. Use the same Topic name (e.g., "sensor/temperature")
3. Use compatible data types (same structure, generated from same IDL)
4. Use compatible QoS (e.g., both RELIABLE or both BEST_EFFORT)

Example: HDDS Publisher → FastDDS Subscriber

HDDS Publisher (Rust):

// Types are generated from IDL using hddsgen (see Generate Types section)
let participant = Participant::builder("hdds_publisher")
    .domain_id(0)
    .with_transport(TransportMode::UdpMulticast)
    .build()?;
let topic = participant.topic::<Temperature>("sensor/temp")?;
let writer = topic.writer().qos(QoS::reliable()).build()?;

writer.write(&Temperature { sensor_id: "s1".into(), value: 23.5 })?;

FastDDS Subscriber (C++):

// Minimal snippet — see full working example in /interop/fastdds/example
auto participant = DomainParticipantFactory::get_instance()->create_participant(0, ...);
auto topic = participant->create_topic("sensor/temp", "Temperature", ...);
auto reader = subscriber->create_datareader(topic, ...);

// Will receive data from HDDS publisher

Verify Interop in 5 Minutes

Already have FastDDS installed? Test cross-vendor communication:

# Terminal 1: HDDS subscriber (from sdk samples)
cd hdds/sdk/samples/01_basics/rust
cargo run --bin hello_world

# Terminal 2: FastDDS publisher (from FastDDS examples)
cd FastDDS/examples/cpp/hello_world
./hello_world publisher

Both sides must use matching types

Cross-vendor interop requires both sides to use types generated from the same IDL file. CDR is a positional format -- field names, types, and order must match exactly.

For a complete working setup with shared IDL, see the FastDDS example.

Detailed Guides

• FastDDS Interop - Step-by-step FastDDS setup
• RTI Connext Interop - RTI configuration
• CycloneDDS Interop - Eclipse CycloneDDS setup
• QoS Translation Matrix - QoS mapping between vendors

Common Issues

Type Mismatch

Ensure both sides use the same IDL definition:

// Both HDDS and FastDDS should use this exact IDL
struct Temperature {
    @key string sensor_id;
    float value;
};

QoS Incompatibility

QoS policies must be compatible for matching:

Writer QoS	Reader QoS	Result
RELIABLE	RELIABLE	Match
RELIABLE	BEST_EFFORT	Match
BEST_EFFORT	RELIABLE	No Match
BEST_EFFORT	BEST_EFFORT	Match

Discovery Issues

If participants don't discover each other:

1. Check firewall settings (ports 7400-7500)
2. Verify multicast is enabled
3. Check domain IDs match
4. Use hdds_viewer to debug traffic