Innovate Motorsports OT-2 SDK - Manual (Page 67)

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So no host network configuration should normally be necessary, aside from connecting to the ad
hoc network above
OK, now that the down and dirty basics are out of the way, it is time to make a pitch for a
little added complexity. Instead of hard coding for the above IP address/port, we
recommend using a ‘Discovery Method’ to find the unit and connect to it.
Discovery basically consists of:
1. Create a UDP (user datagram) socket
2. Set it with broadcast options
3. Broadcast a discovery packet
4. Listen for a response
5. Open a TCP connection using the IP address and port provided in the discovery
response
There are two advantages to this. First, it allows us to change the IP address and port used
without breaking your software. Second, although the unit will only accept one TCP
connection for MTS data at a time, it will always respond to discovery inquiries. If it is
currently being used, it reports that in the response. This lets you distinguish between
failures because of usage conflict and literal ‘device not there’ problems.
For discovery, we use port 0x1936, which is the ‘well known port’ for a protocol called
ArtNet. The discovery packet and response is structured so as not to confuse any actual
ArtNet devices which might be present:
typedef unsigned char U8;
typedef unsigned short U16;
typedef unsigned long U32;
// Protocol ID
#define IMSNET_PROTO_ID "IMS Net"
// Interface Version
#define IMSNET_VERSION (1)
// UDP Discovery Port
#define IMSNET_DISCOVERY (0x1936)
// OpCodes
#define IMSNET_OPCODE_POLL (0x4000)
#define IMSNET_OPCODE_POLLREPLY (0x4100)
// Flags
#define IMSNET_FLAG_INUSE (0x1)
// Poll Structures
#pragma pack ( push )
#pragma pack (1) // must be byte aligned