Fastcode · TrentHouliston · May 25, 2026 · May 26, 2026 · May 26, 2026 · May 26, 2026
diff --git a/.github/workflows/sonarcloud.yaml b/.github/workflows/sonarcloud.yaml
@@ -88,7 +88,7 @@ jobs:
           overwrite: true
 
       - name: SonarQube Scan
-        uses: SonarSource/sonarqube-scan-action@v5
+        uses: SonarSource/sonarqube-scan-action@v8
         if: ${{ !cancelled() }}
         env:
           SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}

diff --git a/docs/explanation/nuclearnet.md b/docs/explanation/nuclearnet.md
diff --git a/docs/how-to/networking.md b/docs/how-to/networking.md
@@ -48,17 +48,17 @@ public:
 };
 ```
 
-### NetworkConfiguration Fields
+### NetworkConfiguration fields
 
-| Field              | Type       | Default    | Description                                     |
-| ------------------ | ---------- | ---------- | ----------------------------------------------- |
-| `name`             | `string`   | —          | Unique name for this node on the network        |
-| `announce_address` | `string`   | —          | Address for node discovery announcements        |
-| `announce_port`    | `uint16_t` | —          | Port for announce messages                      |
-| `bind_address`     | `string`   | `""` (all) | Local interface to bind to                      |
-| `mtu`              | `uint16_t` | `1500`     | Maximum transmission unit (fragments if larger) |
+| Field              | Type       | Default             | Description                                     |
+| ------------------ | ---------- | ------------------- | ----------------------------------------------- |
+| `name`             | `string`   | —                   | Unique name for this node on the network        |
+| `announce_address` | `string`   | `"239.226.152.162"` | Address for node discovery announcements        |
+| `announce_port`    | `uint16_t` | `7447`              | Port for announce messages                      |
+| `bind_address`     | `string`   | `""` (all)          | Local interface to bind to                      |
+| `mtu`              | `uint16_t` | `1500`              | Maximum transmission unit (fragments if larger) |
 
-### Network Modes
+### Network modes
 
 NUClearNet supports several discovery modes depending on the `announce_address` you configure:
 
@@ -226,12 +226,12 @@ public:
 };
 ```
 
-## Reliable vs Unreliable Delivery
+## Reliable vs unreliable delivery
 
-| Mode       | Behavior                                             | Use when                         |
-| ---------- | ---------------------------------------------------- | -------------------------------- |
-| Unreliable | Fire-and-forget. No retransmission. Lowest latency.  | Streaming data, periodic updates |
-| Reliable   | Retransmits until acknowledged. Delivery guaranteed. | Commands, configuration, events  |
+| Mode       | Behavior                                                                          | Use when                         |
+| ---------- | --------------------------------------------------------------------------------- | -------------------------------- |
+| Unreliable | Fire-and-forget. No retransmission. Lowest latency.                               | Streaming data, periodic updates |
+| Reliable   | Retransmits until acknowledged (ACK bitset). Uses Jacobson/Karels RTT estimation. | Commands, configuration, events  |
 
 Pass `true` as the reliability argument to `emit<Scope::NETWORK>`:
 
@@ -243,11 +243,20 @@ emit<Scope::NETWORK>(std::make_unique<Command>(cmd));
 emit<Scope::NETWORK>(std::make_unique<Command>(cmd), true);
 ```
 
-## Serialization Requirements
+## Serialization requirements
 
 Types sent over the network must be serializable.
 NUClear handles this automatically for **trivially copyable** types (POD structs with no pointers or dynamic memory).
 
 For complex types, specialize `NUClear::util::serialise::Serialise<T>` to provide custom `serialise()`, `deserialise()`, and `hash()` methods.
 
 Type safety across nodes is ensured by hash matching — if a type's hash doesn't match between sender and receiver, the message is silently discarded.
+
+## Subscription-based routing
+
+NUClearNet automatically advertises which message types your node is interested in.
+When you register an `on<Network<T>>` reaction, the type hash is added to your node's subscription set and announced to peers.
+Peers will only send messages to your node if you are subscribed to that message type.
+
+If a node has no subscriptions (no `on<Network<T>>` reactions), it receives all messages by default.
+This is useful for debugging or gateway nodes that need to observe all traffic.
diff --git a/docs/reference/dsl/network.md b/docs/reference/dsl/network.md
@@ -41,6 +41,8 @@ sequenceDiagram
 ```
 
 **Bind phase:** Emits a `NetworkListen` message with the type hash of `T` to register interest with the `NetworkController`.
+The hash is also added to this node's subscription set, which is advertised to peers via announce packets.
+Peers use this subscription information to avoid sending messages that no local reaction is listening for.
 
 **Get phase:** Deserializes the message from `ThreadStore` data populated by `NetworkController`, using `Serialise<T>::deserialise()`.
 
@@ -90,6 +92,8 @@ on<Network<SensorReading>>().then([](const NetworkSource& src, const SensorReadi
 - Only reacts to messages received over the network, never to local emits.
 - The type hash is computed from the type name string — renaming a type breaks compatibility with peers using the old name.
 - Multiple nodes can listen for the same type simultaneously.
+- Registering a `Network<T>` reaction causes this node to advertise the type hash as a subscription,
+    enabling subscription-based routing so peers only send relevant messages.
 
 ## See Also
 

diff --git a/docs/reference/emit/network.md b/docs/reference/emit/network.md
@@ -82,9 +82,12 @@ public:
 - Requires `NetworkConfiguration` to be emitted for the network to be active.
 - The type must be serializable: either trivially copyable, or provide a `util::serialise::Serialise<T>` specialization.
 - Type routing uses a hash — the same type must be defined on both peers.
-- If `reliable` is true, delivery is guaranteed (TCP-like semantics).
-    If false, packets may be lost (UDP-like).
+- If `reliable` is true, the message uses ACK-based retransmission with Jacobson/Karels RTO estimation.
+    Retransmissions continue indefinitely until the peer acknowledges or disconnects.
+    If false, packets are fire-and-forget (UDP-like).
 - If the target peer is not connected, the message is silently dropped even with `reliable = true`.
+- Messages are only sent to peers that have subscribed to the type hash (subscription-based routing).
+    Peers with no subscriptions receive all messages by default.
 
 ## See Also
 

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
@@ -28,7 +28,7 @@ configure_file(nuclear.in ${PROJECT_BINARY_DIR}/nuclear)
 
 # Build the library
 find_package(Threads REQUIRED)
-file(GLOB_RECURSE src "*.c" "*.cpp" "*.hpp" "*.ipp")
+file(GLOB_RECURSE src CONFIGURE_DEPENDS "*.c" "*.cpp" "*.hpp" "*.ipp")
 add_library(nuclear STATIC ${src})
 add_library(NUClear::nuclear ALIAS nuclear)
 

diff --git a/src/extension/NetworkController.cpp b/src/extension/NetworkController.cpp
@@ -27,6 +27,8 @@
 #include <cstdint>
 #include <memory>
 #include <mutex>
+#include <set>
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -37,6 +39,8 @@
 #include "../dsl/word/emit/Network.hpp"
 #include "../message/NetworkConfiguration.hpp"
 #include "../message/NetworkEvent.hpp"
+#include "../nuclearnet/Discovery.hpp"
+#include "../nuclearnet/NUClearNet.hpp"
 #include "../util/get_hostname.hpp"
 
 namespace NUClear {
@@ -52,12 +56,13 @@ namespace extension {
         : Reactor(std::move(environment)) {
 
         // Set our function callback
-        network.set_packet_callback([this](const network::NUClearNetwork::NetworkTarget& remote,
-                                           const uint64_t& hash,
-                                           const bool& reliable,
-                                           std::vector<uint8_t>&& payload) {
+        net.set_packet_callback([this](const network::NUClearNet::sock_t& source,
+                                       const std::string& peer_name,
+                                       uint64_t hash,
+                                       bool reliable,
+                                       std::vector<uint8_t>&& payload) {
             // Construct our NetworkSource information
-            const dsl::word::NetworkSource src{remote.name, remote.target, reliable};
+            const dsl::word::NetworkSource src{peer_name, source, reliable};
 
             // Move the payload in as we are stealing it
             const std::vector<uint8_t> p(std::move(payload));
@@ -85,23 +90,23 @@ namespace extension {
         });
 
         // Set our join callback
-        network.set_join_callback([this](const network::NUClearNetwork::NetworkTarget& remote) {
+        net.set_join_callback([this](const network::PeerInfo& peer) {
             auto l     = std::make_unique<message::NetworkJoin>();
-            l->name    = remote.name;
-            l->address = remote.target;
+            l->name    = peer.name;
+            l->address = peer.address;
             emit(l);
         });
 
         // Set our leave callback
-        network.set_leave_callback([this](const network::NUClearNetwork::NetworkTarget& remote) {
+        net.set_leave_callback([this](const network::PeerInfo& peer) {
             auto l     = std::make_unique<message::NetworkLeave>();
-            l->name    = remote.name;
-            l->address = remote.target;
+            l->name    = peer.name;
+            l->address = peer.address;
             emit(l);
         });
 
         // Set our event timer callback
-        network.set_next_event_callback([this](std::chrono::steady_clock::time_point t) {
+        net.set_event_callback([this](std::chrono::steady_clock::time_point t) {
             const std::chrono::steady_clock::duration emit_offset = t - std::chrono::steady_clock::now();
             emit<Scope::DELAY>(std::make_unique<ProcessNetwork>(),
                                std::chrono::duration_cast<NUClear::clock::duration>(emit_offset));
@@ -114,6 +119,9 @@ namespace extension {
 
             // Insert our new reaction
             reactions.insert(std::make_pair(l.hash, l.reaction));
+
+            // Add subscription so peers know to send us this type
+            net.add_subscription(l.hash);
         });
 
         // Stop listening for a network type
@@ -128,13 +136,20 @@ namespace extension {
             if (it != reactions.end()) {
                 reactions.erase(it);
             }
+
+            // Rebuild subscriptions from remaining reactions
+            std::set<uint64_t> subs;
+            for (const auto& r : reactions) {
+                subs.insert(r.first);
+            }
+            net.set_subscriptions(subs);
         });
 
-        on<Trigger<NetworkEmit>>().then("Network Emit", [this](const NetworkEmit& emit) {
-            network.send(emit.hash, emit.payload, emit.target, emit.reliable);
+        on<Trigger<NetworkEmit>>().then("Network Emit", [this](const NetworkEmit& e) {
+            net.send(e.hash, e.payload.data(), e.payload.size(), e.target, e.reliable);
         });
 
-        on<Shutdown>().then("Shutdown Network", [this] { network.shutdown(); });
+        on<Shutdown>().then("Shutdown Network", [this] { net.shutdown(); });
 
         // Configure the NUClearNetwork options
         on<Trigger<NetworkConfiguration>>().then([this](const NetworkConfiguration& config) {
@@ -151,17 +166,32 @@ namespace extension {
                 listen_handles.clear();
             }
 
-            // Name becomes hostname by default if not set
-            const std::string name = config.name.empty() ? util::get_hostname() : config.name;
+            // Build configuration
+            network::NetworkConfig net_config;
+            net_config.name             = config.name.empty() ? util::get_hostname() : config.name;
+            net_config.announce_address = config.announce_address;
+            net_config.announce_port    = config.announce_port;
+            net_config.bind_address     = config.bind_address;
+            net_config.mtu              = config.mtu;
+
+            // Collect current subscriptions
+            {
+                const std::lock_guard<std::mutex> lock(reaction_mutex);
+                std::set<uint64_t> subs;
+                for (const auto& r : reactions) {
+                    subs.insert(r.first);
+                }
+                net.set_subscriptions(subs);
+            }
 
             // Reset our network using this configuration
-            network.reset(name, config.announce_address, config.announce_port, config.bind_address, config.mtu);
+            net.reset(net_config);
 
             // Execution handle
-            process_handle = on<Trigger<ProcessNetwork>>().then("Network processing", [this] { network.process(); });
+            process_handle = on<Trigger<ProcessNetwork>>().then("Network processing", [this] { net.process(); });
 
-            for (auto& fd : network.listen_fds()) {
-                listen_handles.push_back(on<IO>(fd, IO::READ).then("Packet", [this] { network.process(); }));
+            for (auto& fd : net.listen_fds()) {
+                listen_handles.push_back(on<IO>(fd, IO::READ).then("Packet", [this] { net.process(); }));
             }
         });
     }

diff --git a/src/extension/NetworkController.hpp b/src/extension/NetworkController.hpp
@@ -30,8 +30,8 @@
 #include "../PowerPlant.hpp"
 #include "../Reactor.hpp"
 #include "../message/NetworkConfiguration.hpp"
+#include "../nuclearnet/NUClearNet.hpp"
 #include "../util/get_hostname.hpp"
-#include "network/NUClearNetwork.hpp"
 
 namespace NUClear {
 namespace extension {
@@ -42,8 +42,8 @@ namespace extension {
         explicit NetworkController(std::unique_ptr<NUClear::Environment> environment);
 
     private:
-        /// Our NUClearNetwork object that handles the networking
-        network::NUClearNetwork network;
+        /// Our NUClearNet object that handles the networking
+        network::NUClearNet net;
 
         /// The reaction that handles timed events from the network
         ReactionHandle process_handle;