[ENet-discuss] Possible bug - some peers mysteriously disconnecting - help needed
kreso at galacticmag.com
Tue Jan 8 08:43:40 PST 2008
First, sorry for the long post, but the issue might be complex.
I have been using ENET for my game www.galacticmag.com for 2 years.
Since start, I had experienced some strange disconnects. Other than
this, the game and the server are working just fine, it's a
monolythic server and in the last year, other than disconnects,
there are less than 2 bugs monthly, mostly minor stuff.
Now, as I said, I think I have a problem with ENET, but I realize
that I might be wrong.
The problem is that some peers(players) get disconnected for no
apparent reason, the enet connection just breaks down. And it
happens only to a single user at a time, while the 50 other
connected users remain unaffected.
I tried, in the last two years, to find a source of this problem,
but the only thing that could cause the problem seems to be Enet.
There is always that question: Why other Enet users are not getting
the same problem. Perhaps it's because my game requires players to
stay connected for more than hour, so average connection length is
about 50 minutes. If connection breaks, this is immediately noticed
by players because they lose a game.
If the average connection length was lower, there would be lower
percentage of broken connections and this might go unnoticed by
other Enet users. Or perhaps I'm just wrong.
So I recently installed a packet sniffer and captured a short Enet
communication (this log will be provided) which exhibits the problem.
I tried to analyze the log, but this is quite complex, and I
probably wont be able to conclude anything since I don't know enet
So I thought maybe someone knowledgeable could help by analyzing the
log, and perhaps fix the error in the Enet if it exists.
Well, if anyone has time and knowledge I would appreciate the
help... but I understand it is a complex issue and that it might be
too much time consuming.
Enet version: 1.0
Log can be downloaded from:
I think this is some kind of standard sniffer format, but I can view
and analyze it quite nicely with Wireshark.
It's really short, total 207 packets, but the client is disconnected
after first 139. Total length is 6 minutes.
Server's port is 29370, IP 188.8.131.52.
First 20 packets contain one successful Enet connection where user
named LMORRISON creates new account.
Afterwards, there is a second connection that was broken unexpectedly.
Keepalive is implemented on application layer, the client sends the
keepalive packet after 5 seconds of sending nothing. The keepalive
packet consists of a single byte containing the value 5.
Server database reports last keepalive packet was received at the
moment corresponding to approx. 175 seconds into log file.
At the start of the connection, clients sends it's login data,
encrypted, and then communicates lobby chat data with the server.
This lasts up to 5 seconds. The server game event log file confirms
that afteward this, except for the keepalive packets, no other data
was received from client.
Also, not contained in the log file (filtered it out), the client
was clearly disconnected at timestamp 191 because at that point I
received another connection attempt from same IP address, same
username, but different port, meaning that user has restarted the
client and is attempting to reconnect. An then another connection
attempt at timestamp 285. Those were refused by server (no double
logins policy). This also shows that it was probably not the client
simply disconnectiong from internet.
Also, the client's diagnostics show that it is not using NAT.
I actually changed Enet a bit (yes, well..) , but I had the
disconnects before I did the change, in fact, it was attempt to fix
this disconnects by giving clients more time before Enet decides to
drop them, and with more aggressive packet resend strategy. The
changes (made a year ago) are:
-Client: connection is dropped after a fixed time of 150 seconds of
server not acknowledging a packet, and packet resend time is never
higher than 7 seconds.
-Server: connection is dropped on application layer after 175
seconds of no-keepalive, resend time always less than 7 seconds.
Removed Enet built-in keepalive/ping (calls to enet_peer_ping
disabled) on both client and server.
I think that those changes are minimal and could not interfere with
functioning of Enet.
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