diff --git a/core/src/NetSession.cpp b/core/src/NetSession.cpp
index 2b7a9ad..e2ed26d 100644
--- a/core/src/NetSession.cpp
+++ b/core/src/NetSession.cpp
@@ -482,3 +482,70 @@ void NetSession::flushBlockChanges() {
     dirtyLookup.clear();
 }
 
+void NetSession::serviceKeepAlive(uint64_t tick) {
+    if (currentPhase != SessionPhase::Play) return;
+
+    if (tick - lastKeepAliveHeard >= config.keepAliveTimeoutTicks) {
+        keepAliveExpired = true;
+        disconnect("keep alive timeout");
+        return;
+    }
+    if (role != Role::Server) return;
+    if (tick - lastKeepAliveSent < config.keepAliveIntervalTicks) return;
+
+    KeepAlive beat;
+    beat.token = static_cast<int64_t>(tick);
+    PacketWriter body;
+    beat.encode(body);
+    enqueue(PacketId::KeepAlive, body, true);
+    pendingKeepAliveToken = beat.token;
+    lastKeepAliveSent = tick;
+    ++statistics.keepAlivesSent;
+}
+
+void NetSession::flushOutbound() {
+    std::size_t budget = config.bandwidthBytesPerTick;
+    std::size_t used = 0;
+    while (!outbound.empty()) {
+        const QueuedPacket& head = outbound.front();
+        // A packet bigger than the whole budget still goes out once nothing
+        // else has, otherwise it would block the queue forever.
+        if (budget != 0 && used != 0 && used + head.frame.size() > budget) break;
+        if (head.reliable)
+            transport->sendReliable(head.frame);
+        else
+            transport->sendUnreliable(head.frame);
+        used += head.frame.size();
+        statistics.bytesFlushed += head.frame.size();
+        ++statistics.packetsFlushed;
+        outbound.pop_front();
+        if (budget != 0 && used >= budget) break;
+    }
+}
+
+void NetSession::receive(uint64_t tick) {
+    transport->pump(tick);
+    ByteBuffer message;
+    while (transport->popReliable(message)) handleMessage(message, tick);
+    while (transport->popUnreliable(message)) handleMessage(message, tick);
+}
+
+void NetSession::send(uint64_t tick) {
+    if (currentPhase == SessionPhase::Disconnected) return;
+    serviceKeepAlive(tick);
+    if (currentPhase == SessionPhase::Disconnected) return;
+
+    if (role == Role::Server && currentPhase == SessionPhase::Play) {
+        streamChunks();
+        flushBlockChanges();
+    }
+    flushOutbound();
+    transport->flush(tick);
+}
+
+void NetSession::update(uint64_t tick) {
+    receive(tick);
+    send(tick);
+}
+
+} // namespace vf