Unreal Insights includes Networking Insights to analyze, optimize and debug network traffic. Users can record trace information to visualize network behavior with the following features:
- Game Instance control to display visible machines during the network sessions being recorded
- Connection Mode control to visualize outgoing or incoming data
- Packet Overview panel that displays packet timelines (and sizes) being transmitted or received during a game
- Packet Content panel that shows a packet's content, such as replicated objects, properties, and remote function calls
- Net Stats panel that displays trace events for selected packets, including statistics about the total, maximum, and average exclusive (or inclusive) packet sizes.
Setup
Before continuing, ensure that you are running Unreal Insights.
Using Networking Insights
To analyze data start your project instances with the following command-line option:
-NetTrace=[VerbosityLevel] -trace=net
VerbosityLevel should be set to a value of greater than zero. For example, if a game instance starts with -NetTrace=1, Unreal Insights will collect and report network trace data for analysis by opening the session in Unreal Insights.
The editor runs its own data store for trace data, which means that you need to specify the tracehost in order to collect network trace data while running in the editor. To specify the tracehost, use: -NetTrace=1 -tracehost=localhost -trace=net
You can trace simple stats associated with network trace data by using the macros UE_NET_TRACE_PACKET_STATSCOUNTER and UE_NET_TRACE_FRAME_STATSCOUNTER. Data traced with either of these macros will be displayed in the NetStatsCounters tab.
Networking Insights Window
The Networking Insights window is where you'll find networking session data.
For additional commands, tips, and information on other Unreal Insights windows , refer to the Reference documentation.
The Networking Insights window features the Connection Selection panel(1), the Packet Overview panel(2), the Packet Content panel(3), and Net Stats panel(4).
Packet Overview Panel
The Packet Overview panel displays a bar graph that shows the size (in bits) for every packet received or transmitted. This is useful for identifying large packets that need further investigation. Left-click the bar to select a packet.
The reported size of each packet is before compression, so the actual data on the wire may be smaller than what the report shows.
Hovering over a packet displays its information. This information includes:
- Packet Index
- Sequence Number
- Content Size in bits
- Total Size in bytes, with unused bits
- A timestamp for when the packet was sent or received
- The packet's current status (delivered or undelivered)
- The connection state in which the packet was received
- Engine frame number of when the packet was sent or received
Dropped packets are displayed in red. To select multiple packets, click to select an inital packet, then hold the Shift key and click other packets. You can highlight an event in the Packet View, to help you see how many bits that specific event is using in the packet. This makes it possible to quickly see how much bandwidth an event is using relative to other data.
You can choose to highlight either: +The aggregated bitcount for all instances of the event; or +The maximum bitcount used by a single event.
Packet Content Panel
The Packet Content panel displays the actual content of the currently selected packet. The packet's content displays as a hierarchical event graph starting with bit zero on the left side. This is the main tool to investigate the data contents in each packet down to the property level.
The packet content panel displaying bunches of data contained in a packet. This includes information about replicated objects and properties.
The first level displays the bunches contained in a packet. Each bunch is named after the channel that it belongs to. If the reported bunch has its debug name set when reported, the debugname will be used instead of the channelname to provide additional context (where available).
The second level typically displays replicated objects contained in the bunch. If the event has an assigned NetId(NetGUID), the ID is on display as well.
Events further down the event hierarchy display replicated properties, including how many bits they wrote.
Hovering over an event displays all of the event's information.
The panel features controls to find a packet, or to find events belonging to a specific NetId.
You can navigate the Packet Content Panel and Packet Overview Panel using your keyboard. The up and down arrow keys will move between levels. The left and right arrow keys will move between events on the same level. If you hold the CTRL or CMD key and press the left or right arrow keys, you will move between packets.
Connection Selection Panel
The top of the Packet Overview panel has controls that let users select the data to display.
The connection dropdown lists located at the top of the Packet Overview panel. This example shows Player 0's connection in a server game instance, with incoming data selected.
Three dropdown lists are available in the Connection Selection panel:
| Dropdown List | Description |
|---|---|
| Game Instance | Displays the created Game Instance for each unique NetDriver observed during a recording session. For example, when using PIE, there are separate instances for the server and each client. |
| Connection | This dropdown selects a specific connection, displaying every observed connection during the selected Game Instance's session. |
| Connection Mode | This dropdown controls whether to visualize incoming our outgoing data. |
Net Stats Panel
The Net Stats panel lists all trace events for the selected packet range in the Packet Overview panel.
The Net Stats panel with events grouped by level
In addition to aggregating data based on a selected range, users can sort the list in ascending or descending order by the values in any active column. Right-click anywhere in the list to change the sort order, or to activate or deactivate columns. The following columns are available:
- Type
- Level
- Instance Count
- Total Inclusive Size (bits)
- Max Inclusive Size (bits)
- Total Exclusive Size
- Max Exclusive Size
To filter events by name, use the "search net events or groups" field. Users can group according to these event types:
| Group Name | Description |
|---|---|
| Level | Creates one group for each level. |
| Flat | Creates a single group. Includes all Net Events. |
| Name | Creates one group for one letter |
Grouping by Level helps users understand their data better because the same name can appear on different levels. The following table describes these levels:
| Level | Description |
|---|---|
| 0 | Typically channel information that displays all bunches using the channel name. |
| 1 | Replicated Object (Actor), most events at this level show the serialized object. |
| 2 | Reports events originating from property replication or from RPCs. |
| 3 | Reports events when serializing properties. |
| 4 | Reports additional events when serializing properties, array content, and more. |
The Net Stats panel features a !0 toggle to filter out event types that have no data in the selected range.
NetStatsCounters
The NetStatsCounters tab is where you can view stats counters related to the replication system for the selected packet or range of packets.
There are two different categories of stats:
-
FrameStats: Stats counters for the entire frame. This is typically used for reporting stat counters related to networking, for work that is shared between all connections. For example, how many objects are currently being updated on this frame.
-
PacketStats: Stats counters related to each specific packet. For example, how many objects were scheduled to be serialized, and how many actually did fit into the packet.
Example Data
Information about network packet content tracing macro is in the Unreal Insights Reference.
To better understand the data that Networking Insights visualizes, we offer the following examples:
Replicated Objects
This is the initial replication of a new Actor--ReplicationGraphDebugActor, NetGUID 10.
Before the bunch containing the new actor, there is a NetGUID bunch containing all of the exported references from the new Actor, including NetGUIDS.
RPCs
This is an RPC named ClientAckGoodMove that targets PlayerPawn_C with NetGUID 14.
GUIDs must be mapped.
Split Bunches
Event data generated from transmitting a split bunch report with the first part--when receiving a split bunch, parts are reported first, and when all parts are received, events are reported with the final part.
This is a split outgoing bunch. Note that the events in the bunch are larger than the Bunch.
The next few packets look like the following:
SubObjects
This is a SubObject example--note that the second Actor after BotPawn_C shares the same bunch.