91 lines
3.1 KiB
Plaintext
91 lines
3.1 KiB
Plaintext
FCE Ultra 0.91+ network play protocol.
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Description v 0.0.1
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--------------------------------------
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In FCE Ultra, all data is sent to the server, and then the server
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distributes, every emulated frame(60hz on NTSC), the collated data to the
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clients.
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The server should not block when it is receiving UDP data from the clients.
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If no UDP data is available, then just go on.
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The clients MUST block until the input data packet comes on every emulated
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frame.
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Packets from the server to the client are sent out over both TCP and UDP.
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Duplicate packets should be discarded. Out-of-order packets can either
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be cached, or discarded(what I recommend, as caching code gets a little
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complex and wouldn't yield any benefit from what I've observed).
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In the case of client->server UDP communications, the server should just use
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the data from the UDP packet that has the highest packet number count, and
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the server should then set its internal incoming packet counter to that
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number(to prevent out-of-order packets from totally screwing up user input).
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The "magic number"(used with UDP packets) is meant to reduce the chance of a hostile remote host
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from disrupting the network play, without resorting to using extreme amounts
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of network bandwidth. The server generates the magic number, and it is best
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if the magic number is as random as possible.
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UDP packets received with an incorrect magic number should be discarded, of
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course.
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Initialization, server->client:
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uint32 Local UDP port(what the server is listening on).
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uint32 Player number(0-3) for client.
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uint32 Magic number(for UDP).
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Initialization, client->server
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uint32 Local UDP port(that the client is listening on).
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Structure of UDP packet data:
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uint32 CRC32 - Includes magic number, packet counter, and
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data. For reference, CRC32 is calculated
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with the zlib function crc32().
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uint32 Magic number
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uint32 Packet counter(linear, starts at 0).
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uint8[variable] Data.
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Structure of tcp packet data:
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uint32 Packet counter(" ").
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uint8[variable] Data.
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Data format of server->client communications:
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uint8[4] Controller data
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uint8 Command byte. 0 if no command. Otherwise(in decimal):
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1 Select FDS disk side.
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2 Insert/eject FDS disk.
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10 Toggle VS Unisystem dip switch editing.
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11 ... 18 Toggle VS Unisystem dip switches.
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19 Insert VS Unisystem coin.
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30 Reset NES.
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31 Power toggle NES.
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40 Save state(not implemented correctly).
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41 Load state(not implemented correctly).
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42 ... 50 Select save state slot(minus 42).
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Special message communications occurs if the "Packet counter" is
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0xFFFFFFFF(only with TCP):
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uint32 Length of text data, minus the null character(the null
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character is sent, though).
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uint8[variable] Text data. Convert all characters <32 to space, and
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then display the text message(it's one line) as is.
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Structure of client->server communication:
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uint8 Controller data(for this client).
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Over tcp channel, a text message can be sent. It is one line,
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null terminated(remember the data and parse it and display it and
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distribute it to the clients once the null byte is received).
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Maximum size of message(including the null byte) should be 256 bytes.
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