Examples

Learn HDDS through 193 practical examples covering every aspect of DDS. All examples are available in multiple languages: Rust, Python, C++, and C.

SDK Samples

The complete samples collection is available in the HDDS repository:

git clone https://git.hdds.io/hdds/hdds.git
cd hdds/sdk/samples

Sample Categories

Category	Samples	Description
01_basics	21	Hello world, pub/sub fundamentals
02_qos	36	All 22 QoS policies with examples
03_types	62	Every IDL type: structs, enums, sequences, maps, unions
04_discovery	16	SPDP/SEDP, static peers, discovery tuning
05_security	17	Authentication, encryption, access control
06_performance	16	Latency tuning, throughput optimization, benchmarks
07_advanced	16	Waitsets, listeners, content filters, instances
08_interop	3	Cross-vendor communication
09_ros2	3	ROS2 rmw_hdds integration
10_usecases	3	Complete real-world scenarios

Basics

Path: sdk/samples/01_basics/

Example	Languages	Description
hello_world	Rust, Python, C++, C	Minimal pub/sub
pubsub	Rust, Python, C++, C	Basic publisher and subscriber
multiple_topics	Rust, Python	Multiple topics in one participant
participant_config	Rust, Python	Participant configuration options
graceful_shutdown	Rust	Clean shutdown with signal handling

# Run hello world
cd 01_basics/rust && cargo run --bin hello_world
cd 01_basics/python && python hello_world.py

QoS Policies

Path: sdk/samples/02_qos/

Examples for all 22 DDS QoS policies:

Sample	Description	Key QoS
reliable_delivery	Guaranteed delivery with NACK retransmission	`RELIABLE`
best_effort	Fire-and-forget, lowest latency	`BEST_EFFORT`
transient_local	Late-joiner support with historical data	`TRANSIENT_LOCAL`
deadline_monitor	Monitor data update rate violations	`DEADLINE`
liveliness_auto	System heartbeats for presence detection	`LIVELINESS(AUTO)`
liveliness_manual	App-level heartbeat assertion	`LIVELINESS(MANUAL)`
partition_filter	Logical data filtering by namespace	`PARTITION`
ownership_exclusive	Strength-based writer arbitration	`OWNERSHIP(EXCLUSIVE)`
history_keep_last	Retain N most recent samples	`HISTORY(KEEP_LAST)`

QoS Quick Reference

QoS Policy	Options	Use Case
Reliability	RELIABLE / BEST_EFFORT	Guaranteed delivery vs low latency
Durability	VOLATILE / TRANSIENT_LOCAL	Late-joiner data access
History	KEEP_LAST(N) / KEEP_ALL	Sample retention
Deadline	Period duration	Monitor update rate
Liveliness	AUTOMATIC / MANUAL_BY_*	Presence detection
Ownership	SHARED / EXCLUSIVE	Writer arbitration
Partition	String patterns	Logical separation

# Run reliability example
cd 02_qos/rust && cargo run --bin reliability

# Deadline monitoring
./deadline_monitor        # Subscriber
./deadline_monitor pub    # Publisher (meets deadlines)
./deadline_monitor slow   # Publisher (misses deadlines)

# Partition filtering
./partition_filter sub A      # Subscriber in partition "A"
./partition_filter pub A      # Publisher in partition "A" (matches)
./partition_filter pub B      # Publisher in partition "B" (no match)

IDL Types

Path: sdk/samples/03_types/

Every IDL type supported by hdds_gen:

Example	Languages	Types
primitives	Rust, Python, C++	int8, uint32, float, double, bool
strings	Rust, Python	string, bounded string<N>
sequences	Rust, Python	sequence<T>, bounded sequence<T, N>
arrays	Rust, Python	T[N], multidimensional
enums	Rust, Python	enum, @bit_bound
structs	Rust, Python	struct, nested structs
unions	Rust, Python	union with discriminator
maps	Rust, Python	map<K, V>
optional	Rust, Python	@optional fields
bitsets_bitmasks	Rust, Python	bitset, bitmask

# Run sequences example
cd 03_types/rust && cargo run --bin sequences

Discovery

Path: sdk/samples/04_discovery/

Sample	Description
simple_discovery	Automatic participant discovery using SPDP multicast
static_peers	Manual peer configuration for non-multicast networks
discovery_listeners	Callbacks for discovery events (match/unmatch)
partitions	Logical data separation with partition QoS

Partition Matching

Partitions provide logical separation within a domain:

Partition A ────┬──── Partition B
                │
Topic "Data"    │    Topic "Data"
Writer ─────────┼──── Reader (NO MATCH - different partitions)
                │
                │
Partition A ────┴──── Partition A
Topic "Data"         Topic "Data"
Writer ────────────── Reader (MATCH - same partition)

Wildcard matching: * matches any, Sensor* matches SensorA, SensorB, etc.

Network Requirements

Sample	Multicast	Unicast	TCP
simple_discovery	Required	Optional	No
static_peers	Not used	Required	Optional
discovery_listeners	Required	Optional	No
partitions	Required	Optional	No

Security

Path: sdk/samples/05_security/

DDS Security v1.1 examples:

Sample	Description
authentication	PKI-based participant authentication with X.509 certificates
access_control	Governance and permissions for topic-level access control
encryption	Data encryption (AES-GCM) and message authentication (GMAC)
secure_discovery	Authenticated SPDP/SEDP discovery protocol

Security Architecture

┌─────────────────────────────────────────────────────────────┐
│                    Application Layer                         │
├─────────────────────────────────────────────────────────────┤
│                      DDS Layer                               │
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐          │
│  │ DataWriter  │  │ DataReader  │  │  Discovery  │          │
│  └──────┬──────┘  └──────┬──────┘  └──────┬──────┘          │
├─────────┴────────────────┴────────────────┴─────────────────┤
│                   Security Plugins                           │
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐          │
│  │Authentication│  │Access Control│  │Cryptography │          │
│  │   Plugin    │  │   Plugin    │  │   Plugin    │          │
│  └─────────────┘  └─────────────┘  └─────────────┘          │
├─────────────────────────────────────────────────────────────┤
│                    Transport Layer                           │
│              (UDP/TCP with TLS optional)                     │
└─────────────────────────────────────────────────────────────┘

Protection Levels

Level	Confidentiality	Integrity	Overhead
NONE	No	No	0 bytes
SIGN (GMAC)	No	Yes	16 bytes
ENCRYPT (GCM)	Yes	Yes	16 bytes
SIGN+ENCRYPT	Yes	Yes	32 bytes

Performance

Path: sdk/samples/06_performance/

Sample	Description
latency	Ping-pong latency measurement with histograms
throughput	Maximum messages/sec and MB/sec benchmarks
batching	Message batching for improved throughput
zero_copy	Shared memory for eliminating data copies

Performance Metrics

Metric	Small (64B)	Medium (1KB)	Large (64KB)
Latency	~50 us	~75 us	~200 us
Throughput	1M msg/s	500K msg/s	50K msg/s
Bandwidth	64 MB/s	500 MB/s	3.2 GB/s

Batching Efficiency

Configuration	Packets	Efficiency
No batching	10,000	1.0x
Batch 1KB	640	15.6x
Batch 8KB	80	125x
Batch 64KB	10	1000x

Tuning Tips

For low latency:

Reduce/disable batching
Pin threads to CPU cores
Use UDP transport
Set real-time priority

For high throughput:

Enable batching (8KB-64KB)
Use zero-copy for large payloads
Increase history depth
Tune socket buffers

Advanced

Path: sdk/samples/07_advanced/

Sample	Description
content_filter	SQL-like content filtering for efficient data subscription
request_reply	RPC-style communication patterns over DDS
waitsets	Condition-based event handling and multiplexing
dynamic_data	Runtime type manipulation and introspection

WaitSet Architecture

  ┌─────────────────────────────────────────┐
  │               WaitSet                   │
  │  ┌───────────┐ ┌───────────┐           │
  │  │ ReadCond  │ │ StatusCond│           │
  │  │ (Topic A) │ │ (Reader)  │           │
  │  └───────────┘ └───────────┘           │
  │  ┌───────────┐ ┌───────────┐           │
  │  │ GuardCond │ │ ReadCond  │           │
  │  │ (Shutdown)│ │ (Topic B) │           │
  │  └───────────┘ └───────────┘           │
  └─────────────────────────────────────────┘
                    │
                    ▼
              wait(timeout)
                    │
                    ▼
         Active Conditions List

Condition Types

Type	Trigger	Use Case
`ReadCondition`	Data available	Data reception
`StatusCondition`	Entity status changed	Liveliness, matches
`GuardCondition`	Application signal	Shutdown, inter-thread
`QueryCondition`	Filtered data available	Content-filtered reads

Content Filter Expressions

temperature > 30.0           -- Comparison
location = 'ServerRoom'      -- Equality
sensor_id BETWEEN 1 AND 10   -- Range
humidity > %0                -- Parameter reference
location LIKE 'Building%'    -- Pattern matching
temp > 25 AND hum > 60       -- Logical operators

Interoperability

Path: sdk/samples/08_interop/

Example	Description
hdds_to_fastdds	HDDS publisher → FastDDS subscriber
hdds_to_rti	HDDS ↔ RTI Connext
hdds_to_cyclone	HDDS ↔ CycloneDDS

ROS2 Integration

Path: sdk/samples/09_ros2/

Example	Description
rmw_hdds_talker	ROS2 publisher with rmw_hdds
rmw_hdds_listener	ROS2 subscriber with rmw_hdds
mixed_dds_ros2	Native HDDS + ROS2 nodes

Real-World Use Cases

Path: sdk/samples/10_usecases/

Example	Description
autonomous_vehicle	LiDAR, camera, control topics
industrial_iot	Sensor mesh with edge gateway
robotics_swarm	Multi-robot coordination

Building All Samples

cd sdk/samples

# Build all Rust samples
./build.sh rust

# Build all C++ samples
./build.sh cpp

# Build all
make all

Contributing Examples

Want to add an example? See the contribution guide.

SDK Samples​

Sample Categories​

Basics​

QoS Policies​

QoS Quick Reference​

IDL Types​

Discovery​

Partition Matching​

Network Requirements​

Security​

Security Architecture​

Protection Levels​

Performance​

Performance Metrics​

Batching Efficiency​

Tuning Tips​

Advanced​

WaitSet Architecture​

Condition Types​

Content Filter Expressions​

Interoperability​

ROS2 Integration​

Real-World Use Cases​

Building All Samples​

Contributing Examples​