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InSim Relay client information (old)
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InSim Relay client information (old)
-- InSim Relay usage information --

The InSim Relay is a service that can connect to your LFS host via InSim and relay the InSim information sent by your host, to anyone who connects to the InSim Relay. This relayed data can be used by programmers for various things, such as the LFS Spectator (remote viewing of a race) and race-tracking to store race information and statistics.

To have your host connected to the Relay, see this page on LFS World:

The rest of this document is only for programmers who want to know how to connect with the InSim Relay, so they can make use of the available data.
-NEW : you can now also connect various other insim mods via the relay, because you can 'connect' to a host with an admin password. See the bottom of this document for which packets are allowed to send.

Connecting to the InSim Relay

The network protocol used with the Relay is UDP and it is located at port 47474

Connecting to the Relay is done with the CCN packet. To connect, make sure bit 0 of the flags is set, which means 'connect to relay'.
The CCN packet is a multifunctional packet. It is used to connect to the Relay, request a list of available hosts and set various options.
Here is the struct of the connection packet:

struct ClientConnection
char Id [4]; // CCN + zero (\0)
byte Flags; // Bit flags for options and 'connect' flag
byte Spare; // spare1
byte Spare; // spare2
byte Spare; // spare2

Flags in CCN packet:
#define ISR_CONNECT 1 // bit 0 : 'connect' flag. Must be set to connect to Relay
#define ISR_HOSTLIST 2 // bit 1 : if set, you will get a list of hosts returned
#define ISR_NOMCI 4 // bit 2 : if set, you will not receive MCI packets
#define ISR_VERIFY 8 // bit 3 : if set, 'guaranteed delivery' will be on

The CCN packet with bit 0 set _must_ be your first packet, otherwise your packets will be ignored. To acknowledge that the connection was successful, an ACK packet is sent, if you didn't already request a hostlist in your initial CCN packet.
You can additionally send a CCN packet at any time, to toggle NOMCI and/or VERIFY and to request a hostlist even while still being connected to a host.
A note about guaranteed delivery; it works exactly like with normal InSim guaranteed delivery, so if you don't know how it works, please look in the Insim.txt that comes with LFS.

There is one official case where connecting might fail; when the Relay has reached its maximum number of users.
In that case, the Relay will send an ERR packet. The ERR packet also has some other error message purposes.

struct ErrorMessage
char Id [4]; // ERR + zero
byte ErrNo; // number of the error
byte Spare; // spare1
byte Spare; // spare2
byte Spare; // spare2

ErrNo meanings:
1 - Invalid Spectatorpassword given
2 - Relay has reached maximum number of clients
3 - Non-existent hostname given in HOS packet

Receiving the hostlist

When you have requested a list of hosts with bit 1 of the flags in the CCN packet, you will receive a list of hosts. The result packet(s) is/are identified by the CHL id. Every CHL packet contains a maximum of 8 hosts and their respective information. If there are more than 8 hosts available to select from, you will receive multiple CHL packets. You can determine how many CHL packets you should expect by reading the 'total hosts' word in every CHL packet (this number is the same in every CHL packet). You can determine the amount of hosts listed in a CHL packet, by the length of the packet.

struct ClientgetHostList
char Id [4]; // CHL + zero
word NrHosts; // Number of total available hosts
byte Spare; // Spare1
byte Spare; // Spare2
char Host [32]; // Hostname(s) (min: 1 / max 8 hostnames - check the length of this packet)
byte NrRacers; // Number of racers on a host
byte Specpass; // 1 if host requires a spectator password

An example of the order things in this packet:
3 hosts listed in this packet:


host1 has 4 racers and requires a specpass
host2 has 2 racers and required a specpass
host3 has 1 racer and does not require a specpass

Select a host to receive InSim data from

To start receiving InSim packets from a host, you must select the host with a HOS packet:

struct SelectHost
char Id [4]; // HOS + zero
char Host [32]; // hostname
char Specpass[24]; // spectator password
char Adminpass[16]; // admin password

Note that both the full hostname and ^-stripped/converted hostname can be used.

ex. "^1EXAMPLE^v^7HOST ^11" or "EXAMPLE|HOST 1"

Maintaining a connection to the Relay

If the relay has not received any data from a client in 60 seconds, the Relay will close the connection with the client. To prevent this from happening, the client can send ACK packets every 20 seconds, in case nothing else has been sent to the Relay.

struct Acknowledge
char Id [4]; // ACK + zero

If you need to, you can optionally add 4 null bytes, but it's not required for the relay to recognise the ACK packet.

The same goes for the other way around. The Relay will send ACK packets to your client in case nothing has been sent in 20 seconds. You can make your client assume that the Relay is offline, if you didn't receive anything from the relay during 60 seconds.

Closing a connection (client side)

When the client closes, it's nice to have it send a 'close' instruction to the Relay:

struct ClientClose
char Id [4]; // ISC + zero

If you need to, you can optionally add 4 null bytes, but it's not required for the relay to recognise the ISC packet.

Closing a connection (relay side)

If the relay needs to "close" your connection for whatever reason or if the relay goes offline, it will send a packet to notify that you will need to try to connect again with the CCN packet.

struct ClientTerminate
char Id [4]; // CTM + zero

Public requests for host information

A client can request some information from a host by sending the relay one of the following InSim packets:


These packets are regular InSim packets, so for their structs, please see the insim.txt file included with every distribution of S2 or the S2 dedicated host.

Admin-only control packets

If you have connected to a host with the adminpassword set (in the HOS packet), you are allowed to send some control packets:


These packets are regular InSim packets, so for their structs, please see the insim.txt file included with every distribution of S2 or the S2 dedicated host.
Attached files
insim_relay.txt - 6.8 KB - 510 views
one note - i know the CHL packet struct isn't an official struct (it wouldn't work as it does in c++ or so), but it's been like that from the start, so it's the idea that counts and it does work If you can't get a grasp on it, just ask and I'll try to explain.
Very cool. Can't wait to see what people come up with using this.

It'll probably be a couple of weeks before i have the time to get the new methods into my Lib to let it work seamlessly as a relay client.
Yay, relay's back! Victor, you rule and Scawen rock :
two updates:

1) in the CCN packet, guaranteed delivery (like with regular insim) can be enabled (for you stats boys ).

2) in the HOS packet both full hostnames and ^-stripped/converted hostnames can be used.

See the first post for more details.
Quote from CrazyICE :and eric....?

thx vic!

He's the artist, he has drawn the picture! d'oh! )
#8 - wabz
Can NCN requests be sent through the relay too please?

p.s. is the beginnings of a patch against 0.11b of sdether's insim library which adds connecting/messages through relay functionality. It works, but doesn't do everything it should - throw exceptions on errors etc. Browse For Speed 0.5's LFSLib.dll is built with that patch.
Can the timescale of the 15 relay reconnection attempts be rescaled please?

When there is an outage it seems that if your server ( or in todays case, LFS World ) is not back up and running in a few minutes then the server owners have to re-establish the link again - I seem to have to re-establish the link quite often, and think it would help massively if the 15 reconnect attempts occur over a period of 1 day.

Thank you.
edited by Gunn
I beg of you, make a pit InSim packet for your up coming V patches.
Hi, in wich intervall are the MCI packets going to be send?

EDIT: fine intervall is 500ms
Are the relay packets going to be updated for the new version?
I haven't used the Relay before, but want to include it in the next version of LFSLib.NET. Is it currently up and running for patch X, using the old relay packets or should I be waiting for the relay to catch up to X?

Any word on when the Relay page will be updated for X and working again?

i was working on it before the competitions started. But then I had to get onto the competitions and some other things, so insim relay development got paused. I hope to continue it again later this month. Shouldn't take too long anymore to finish it, though it'll also need a bit of testing to check if it's all ok. It's totally rewritten, so there may be bugs .. hence the need for testing.
Does anyone have, or is working on an application for use with the (new) relay?

I'm currently at the point at which it could do with some more testing and feedback, to see if it works and if it has the functionality it should have for proper use.

If you want to start supporting the relay, you should read the following documentation. It's basically an addition to regular InSim, so it should be reasonably easy to support the relay. You can also send it the regular InSim requests. Connection maintenance is also the same - you should make sure that your application sends something to the relay every 20-30 seconds.

The main differences is that the ISI packet is not used, but instead you select a host with the IR_SEL (InsimRelaySelect) packet.
Also you cannot use _every_ available packet - for example things related to OutGage / OutSim enabling are ignored by the relay.

Docs : (temporary)

// InSimRelay for LFS InSim version 4 (LFS 0.5X and up)
// Connect your client to with TCP ( during testing)
// After you are connected you can request a hostlist, so you can see
// which hosts you can connect to.
// Then you can send a packet to the Relay to select a host. After that
// the Relay will send you all insim data from that host.

// Some hosts require a spectator password in order to be selectable.

// You do not need to specify a spectator password if you use a valid administrator password.

// If you connect with an administrator password, you can send just about every
// regular InSim packet there is available in LFS, just like as if you were connected
// to the host directly. For a full list, see end of document.

// Packet types used for the Relay

#define IRP_HLR 252 // Send : To request a hostlist
#define IRP_HOS 253 // Receive : Hostlist info
#define IRP_SEL 254 // Send : To select a host
#define IRP_ERR 255 // Receive : An error number

// To request a hostlist from the Relay, send this packet :

struct IR_HLR // HostList Request
byte Size; // 4
byte Type; // IRP_HLR
byte ReqI;
byte Sp0;

// That will return (multiple) packets containing hostnames and some information about them

// The following struct is a subpacket of the IR_HOS packet

struct HInfo // Sub packet for IR_HOS. Contains host information
char HName[32]; // Name of the host - can be colourcode stripped

char Track[6]; // Short track name
byte Flags; // Info flags about the host - see NOTE 1) below
byte NumConns; // Number of people on the host

// NOTE 1)

#define HOS_SPECPASS 1 // Host requires a spectator password

struct IR_HOS // Hostlist (hosts connected to the Relay)
byte Size; // 4 + NumHosts * 40
byte Type; // IRP_HOS
byte ReqI; // As given in IR_HLR
byte NumHosts; // Number of hosts described in this packet

HInfo Info[6]; // Host info for every host in the Relay. 1 to 6 of these in a IR_HOS

// To select a host in the Relay, send this packet :

struct IR_SEL // Relay select - packet to select a host, so relay starts sending you data.
byte Size; // 68
byte Type; // IRP_SEL
byte ReqI; // If non-zero Relay will send an IS_VER packet
byte Zero; // 0

char HName[32]; // Hostname to receive data from
char Admin[16]; // Admin password (to gain admin access to host)
char Spec[16]; // Spectator password (if host requires it)


// If you specify a wrong value, like invalid packet / hostname / adminpass / specpass,
// the Relay returns an error packet :

struct IR_ERR
byte Size; // 4
byte Type; // IRP_ERR
byte ReqI; // As given in RL_SEL, otherwise 0
byte ErrNo; // Error number - see NOTE 2) below

// NOTE 2) Error numbers :

#define IR_ERR_PACKET 1 // Invalid packet sent by client (wrong structure / length)
#define IR_ERR_PACKET2 2 // Invalid packet sent by client (packet was not allowed to be forwarded to host)
#define IR_ERR_HOSTNAME 3 // Wrong hostname given by client
#define IR_ERR_ADMIN 4 // Wrong admin pass given by client
#define IR_ERR_SPEC 5 // Wrong spec pass given by client

Regular insim packets that a relay client can send to host :

For anyone

Admin only

The relay will also accept, but not forward
TINY_NONE // for relay-connection maintenance

feel free to comment or ask for additional features.

I'll be implementing Relay support into my library, but I probably won't have anything ready for testing until next week. I'll PM you once I have something I can test with.

But you best just drop a msg here then and I'll contact you. My pm's are turned off Connection timed out: connect

I cannot connect to; Even with putty the connection just times out.
Are you using tcp? And using port 47474 for sure?

I saw someone else connect, so it should be possible. works for me. At least I can telnet to it and open the channel. Haven't tried sending packets
Quote from Victor :Are you using tcp? And using port 47474 for sure?

I saw someone else connect, so it should be possible.

Sometimes I just hate java :bitehard:
added additional admin-only packet types (packets that the relay will accept from client and relay to host). See the documentation in my post above.

also the test relay is connected to the south city lx month host, so tehre's some activity to test with.
Just two thoughts for now:
- Use the fourth byte in the IR_ERR packet for the error code
- Allow TINY_NONE replies to TINY_NONE packets received from the relay

Both to make it more consistent with the normal insim.
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InSim Relay client information (old)
(67 posts, closed, started )