diff --git a/catkit_core/MessageBroker.cpp b/catkit_core/MessageBroker.cpp
index d3ee1776..1fc6df6d 100644
--- a/catkit_core/MessageBroker.cpp
+++ b/catkit_core/MessageBroker.cpp
@@ -26,3 +26,155 @@ void TopicHeader::CopyFrom(const TopicHeader &header)
 	std::copy(header.message_offsets, header.message_offsets + TOPIC_MAX_NUM_MESSAGES, message_offsets);
 	std::copy((char *)header.metadata_keys, (char *)header.metadata_keys + sizeof(metadata_keys), (char *)metadata_keys);
 }
+
+Message MessageBroker::PrepareMessage(const std::string &topic, size_t payload_size, int8_t device_id)
+{
+	Uuid trace_id;
+	m_UuidGenerator.Generate(trace_id);
+
+	return PrepareMessage(topic, trace_id, payload_size, device_id);
+}
+
+Message MessageBroker::PrepareMessage(const std::string &topic, Uuid trace_id, size_t payload_size, int8_t device_id)
+{
+	Message message;
+
+	message.m_HasBeenPublished = false;
+	message.m_MessageBroker = shared_from_this();
+
+	// Allocate a payload.
+	auto allocator = GetAllocator(device_id);
+
+	if (allocator == nullptr)
+	{
+		throw std::runtime_error("Invalid device ID.");
+	}
+
+	auto block_handle = allocator->Allocate(payload_size);
+
+	if (block_handle == FreeListAllocator::INVALID_HANDLE)
+	{
+		throw std::runtime_error("Could not allocate payload.");
+	}
+
+	auto offset = allocator->GetOffset(block_handle);
+
+	if (device_id < 0)
+	{
+		message.m_Payload = m_CpuPayloadMemory->GetAddress() + offset;
+	}
+	else
+	{
+		message.m_Payload = m_GpuPayloadMemory[device_id]->GetAddress() + offset;
+	}
+
+	// Allocate a message header.
+	auto message_header_handle = m_MessageHeaderAllocator.Allocate();
+
+	if (message_header_handle == PoolAllocator::INVALID_HANDLE)
+	{
+		throw std::runtime_error("Could not allocate message header.");
+	}
+
+	// Access the message header.
+	message.m_Header = &m_MessageHeaders[message_header_handle];
+	auto header = message.m_Header;
+
+	// Set the payload information.
+	header->payload_info.device_id = device_id;
+	header->payload_info.total_size = payload_size;
+	header->payload_info.offset_in_buffer = offset;
+	m_UuidGenerator.Generate(header->payload_id);
+
+	// Set the topic.
+	std::strncpy(header->topic, topic.c_str(), sizeof(header->topic));
+
+	// Set the trace ID.
+	std::strncpy(header->trace_id, trace_id, sizeof(header->trace_id));
+
+	// Set the producer information.
+	std::strncpy(header->producer_hostname, GetHostName().c_str(), sizeof(header->producer_hostname));
+	header->producer_pid = GetProcessId();
+
+	header->partial_frame_id = 0;
+	header->start_byte = 0;
+	header->end_byte = payload_size;
+
+	// Set default values.
+	header->frame_id = INVALID_FRAME_ID;
+	header->producer_timestamp = 0;
+
+	return message;
+}
+
+void MessageBroker::PublishMessage(Message &message, bool is_final)
+{
+	if (message.m_HasBeenPublished)
+	{
+		return;
+	}
+
+	auto topic_header = m_TopicHeaders.Find(message.m_Header->topic);
+
+	if (message.m_Header->partial_frame_id == INVALID_FRAME_ID)
+	{
+		// First partial frame. Assign a new frame ID.
+		message.m_Header->frame_id = topic_header->next_frame_id.fetch_add(1, std::memory_order_relaxed);
+		message.m_Header->partial_frame_id = 0;
+	}
+	else
+	{
+		// Not the first partial frame. Use the same frame ID and increment the partial frame ID.
+		message.m_Header->partial_frame_id++;
+	}
+
+	// Get timestamp.
+	message.m_Header->producer_timestamp = GetTimeStamp();
+
+	// Go to synchronization structures and signal them.
+
+
+	if (!is_final)
+	{
+		// Copy the message header since it's gone after publishing.
+		auto message_header_handle = m_MessageHeaderAllocator.Allocate();
+
+		if (message_header_handle == PoolAllocator::INVALID_HANDLE)
+		{
+			throw std::runtime_error("Could not allocate message header.");
+		}
+
+		auto new_message_header = &m_MessageHeaders[message_header_handle];
+		*new_message_header = *message.m_Header;
+		message.m_Header = new_message_header;
+	}
+
+	message.m_HasBeenPublished = is_final;
+}
+
+FreeListAllocator *MessageBroker::GetAllocator(int8_t device_id)
+{
+	if (device_id < -1 || device_id >= MAX_NUM_GPUS)
+	{
+		return nullptr;
+	}
+
+	if (device_id == -1)
+	{
+		return &m_CpuPayloadAllocator;
+	}
+
+	return &m_GpuPayloadAllocator[device_id];
+}
+
+Synchronization *MessageBroker::GetSynchronization(const std::string &topic)
+{
+	auto topic_header = m_TopicHeaders.Find(topic);
+
+	if (topic_header == nullptr)
+	{
+		return nullptr;
+	}
+
+	// TODO: look up the synchronization structure (not the shared data).
+}