[robocup-small] New Referee Box Protocol
Joydeep Biswas
joydeep at cmu.edu
Fri Nov 9 09:27:46 EST 2012
Hi Chris & the rest of the TC,
It's good to see the referee protocol be modernized. I have a couple
of recommendations:
1. The time stamp should be a double precision float (float64), in
terms of epoch time in seconds. This will allow precision of up to
fractions of microseconds (see calculation [1]), and can be used for
time comparisons much more easily. Code for GetTimeSec() in [2]. These
time stamps are only as meaningful as the synchronization of the
clocks between the computers. Therefore, I recommend that the referee
computer be configured to run ntpd. Teams can then sync times with the
referee.
2. We should move to TCP. The additional couple of microseconds of
latency is a minuscule price to pay for the reliability gain.
Regards,
Joydeep
[1] Current epoch time in seconds (only order of magnitude important),
divided by 2^(mantissa bits) = 1352471098 / (2^52) = 0.3 usec
[2]
double GetTimeSec() {
timespec ts;
clock_gettime(CLOCK_REALTIME,&ts);
return( static_cast<double>(ts.tv_sec) +
static_cast<double>(ts.tv_nsec)*(1.0E-9));
}
On Fri, Nov 9, 2012 at 2:39 AM, Christopher Head <chead at chead.ca> wrote:
>
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> Hello teams!
> I have been doing a bunch of work on the referee box. One of the things
> I would like to do is improve its network protocol, as there are a
> number of things it doesn’t handle as well as it could—some
> information is not exposed sensibly, and some information is not
> exposed at all. I therefore propose that the referee box output a new
> network protocol based on Google Protobuf—this should be no problem for
> anyone since you all have to receive SSL-Vision data using Protobuf
> anyway. Of course, for those who don’t want to modify their code right
> away, the referee box will still send out the old data format as
> well—it will send both formats, on different multicast groups and
> different UDP ports.
>
> I propose that the new referee box packets follow the schema at the
> bottom of this e-mail.
>
> Comments are welcome. If you can think of anything else you’d like to
> see, please reply, either to the list or to me personally.
>
> Thanks!
> Chris
> SSL TC Chair
>
>
>
> // Each UDP packet contains one of these messages.
> message Referee {
> // The UNIX timestamp when the packet was sent, in milliseconds.
> // Divide by 1000 to get a time_t.
> required uint64 timestamp = 1;
>
> // These are the "coarse" stages of the game.
> enum Stage {
> // The first half is about to start.
> // A kickoff is called within this stage.
> // This stage ends with the NORMAL_START.
> NORMAL_FIRST_HALF_PRE = 0;
> // The first half of the normal game, before half time.
> NORMAL_FIRST_HALF = 1;
> // Half time between first and second halves.
> NORMAL_HALF_TIME = 2;
> // The second half is about to start.
> // A kickoff is called within this stage.
> // This stage ends with the NORMAL_START.
> NORMAL_SECOND_HALF_PRE = 3;
> // The second half of the normal game, after half time.
> NORMAL_SECOND_HALF = 4;
> // The break before extra time.
> EXTRA_TIME_BREAK = 5;
> // The first half of extra time is about to start.
> // A kickoff is called within this stage.
> // This stage ends with the NORMAL_START.
> EXTRA_FIRST_HALF_PRE = 6;
> // The first half of extra time.
> EXTRA_FIRST_HALF = 7;
> // Half time between first and second extra halves.
> EXTRA_HALF_TIME = 8;
> // The second half of extra time is about to start.
> // A kickoff is called within this stage.
> // This stage ends with the NORMAL_START.
> EXTRA_SECOND_HALF_PRE = 9;
> // The second half of extra time.
> EXTRA_SECOND_HALF = 10;
> // The break before penalty shootout.
> PENALTY_SHOOTOUT_BREAK = 11;
> // The penalty shootout.
> PENALTY_SHOOTOUT = 12;
> // The game is over.
> POST_GAME = 13;
> }
> required Stage stage = 2;
>
> // The number of seconds left in the stage.
> // The following stages have this value; the rest do not:
> // NORMAL_FIRST_HALF
> // NORMAL_HALF_TIME
> // NORMAL_SECOND_HALF
> // EXTRA_TIME_BREAK
> // EXTRA_FIRST_HALF
> // EXTRA_HALF_TIME
> // EXTRA_SECOND_HALF
> // PENALTY_SHOOTOUT_BREAK
> //
> // If the stage runs over its specified time, this value stays
> // at zero until the stage ends.
> required uint32 stage_time_left = 3;
>
> // These are the "fine" states of play on the field.
> enum Command {
> // All robots should completely stop moving.
> HALT = 0;
> // Robots must keep 50 cm from the ball.
> STOP = 1;
> // A prepared kickoff or penalty may now be taken.
> NORMAL_START = 2;
> // The ball is dropped and free for either team.
> FORCE_START = 3;
> // The yellow team may move into kickoff position.
> PREPARE_KICKOFF_YELLOW = 4;
> // The blue team may move into kickoff position.
> PREPARE_KICKOFF_BLUE = 5;
> // The yellow team may move into penalty position.
> PREPARE_PENALTY_YELLOW = 6;
> // The blue team may move into penalty position.
> PREPARE_PENALTY_BLUE = 7;
> // The yellow team may take a direct free kick.
> DIRECT_FREE_YELLOW = 8;
> // The blue team may take a direct free kick.
> DIRECT_FREE_BLUE = 9;
> // The yellow team may take an indirect free kick.
> INDIRECT_FREE_YELLOW = 10;
> // The blue team may take an indirect free kick.
> INDIRECT_FREE_BLUE = 11;
> // The yellow team is currently in a timeout.
> TIMEOUT_YELLOW = 12;
> // The blue team is currently in a timeout.
> TIMEOUT_BLUE = 13;
> // The yellow team just scored a goal.
> // For information only.
> // For rules compliance, teams must treat as STOP.
> GOAL_YELLOW = 14;
> // The blue team just scored a goal.
> GOAL_BLUE = 15;
> }
> required Command command = 4;
>
> // The number of commands issued since startup (mod 2^32).
> required uint32 command_counter = 5;
>
> // Information about a single team.
> message TeamInfo {
> // The number of goals scored by the team.
> required uint32 score = 1;
> // The number of red cards issued to the team
> // since the beginning of the game.
> required uint32 red_cards = 2;
> // The amount of time (in seconds) left on each yellow
> // card issued to the team.
> // If no yellow cards are issued, this array has no
> // elements.
> // Otherwise, ordered from smallest to largest.
> repeated uint32 yellow_card_times = 3;
> // The number of timeouts this team can still call.
> // If in a timeout right now, that timeout is excluded.
> required uint32 timeouts = 4;
> // The number of seconds of timeout this team can use.
> required uint32 timeout_time = 5;
> }
>
> // Information about the two teams.
> required TeamInfo yellow = 6;
> required TeamInfo blue = 7;
> }
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