Howto:Record, analyze and replay multiplayer flights with network tools: Difference between revisions

{{Note|As of 2020-August, Flightgear next has built-in support for recording/replaying multiplayer aircraft.}}

With wireshark we can now extract some pilot(s), use a certain time interval of traffic, or see certain traffic properties.

Here is a wireshark analysis showing the multiplayer packet rate for different multiplayer pilots from a recorded multiplayer session.

Until now I either use an other PC to send traffic back to my FlightGear PC, or i send to the internet box's external IP  address, with a redirection to my pc for the port used in its firewall.

It is up to you to find your MAC and IP address. You can use wireshark on some network traffic between the two, or ifconfig on Linux etc. Here is the "magic" line,

* -C force a checksum recalculation. If not the packets are not valid and are not sent.

* --enet-smac gives the mac address of the sender

* --enet-dmac same with the receiver

* -S changes source IP address

* -D does the same for destination

* -i input file (the previously recorded flight)

* -o output file

Now we start FlightGear with Multiplayer enabled by sending to a server (it can be a MPserver or the address of a valid local host on your network, for example 192.168.0.17).

Tcpreplay works fine this way if we don't need a very good time flow sync, as it end being late, dépending on the cpu usage mostly. I didn't notice this issue at first, but this became evident using lag statistics available recently in next, so to keep a good sync between tcpreplay and flightgear, using a core affinity, setting a priority higher and preferably on a not overloaded PC/CPU core makes things better, so we got something like that on linux:

The "-x" option (time acceleration) ensure a good time sync over the replay (find yourself the best value for your config :) ), i just need to adjust the time offset for the mp clock, to have replayed planes in sync with my session, considered as "real time" buddys.

[[File:Fighters mont aiguille.jpg|thumb|The "mont aiguille", in the French Vercors Massif.]]

if you don't have time to make a record yourself, you can use this [http://janodesbois.free.fr/flightgear/cap_files/vercors_test.cap.bz2 flight in the French Vercors Massif] (3.4M). Start at LFLU, runway 01 with the [[UFO]] or in a plane capable of more than 400 kts, and follow the leading [[McDonnell F-4 Phantom II|F-4N]] in a Vercors Massif trip, followed by a [[English Electric Lightning|Lightning]], a [[General Dynamics F-16 Fighting Falcon|F-16]] and a [[Grumman F-14 Tomcat|F-14B]]. It is better with a detailed scenery like "La France d'el maxo".