using System;

​

Transition[] events = { Transition.APP_PASSIVE_OPEN, Transition.APP_SEND, Transition.RCV_SYN_ACK };

​

State state = State.CLOSED;

foreach (Transition @event in events)

{

    state = (state, @event) switch

    {

        (State.CLOSED, Transition.APP_PASSIVE_OPEN) => State.LISTEN,

        (State.CLOSED, Transition.APP_ACTIVE_OPEN) => State.SYN_SENT,

        (State.LISTEN, Transition.RCV_SYN) => State.SYN_RCVD,

        (State.LISTEN, Transition.APP_SEND) => State.SYN_SENT,

        (State.LISTEN, Transition.APP_CLOSE) => State.CLOSED,

        (State.SYN_RCVD, Transition.APP_CLOSE) => State.FIN_WAIT_1,

        (State.SYN_RCVD, Transition.RCV_ACK) => State.ESTABLISHED,

        (State.SYN_SENT, Transition.RCV_SYN_ACK) => State.SYN_RCVD,

        (State.SYN_SENT, Transition.APP_CLOSE) => State.ESTABLISHED,

        (State.SYN_SENT, Transition.RCV_ACK) => State.CLOSED,

        (State.ESTABLISHED, Transition.APP_CLOSE) => State.FIN_WAIT_1,

        (State.ESTABLISHED, Transition.RCV_FIN) => State.CLOSE_WAIT,

        (State.FIN_WAIT_1, Transition.RCV_FIN) => State.CLOSING,

        (State.FIN_WAIT_1, Transition.RCV_FIN_ACK) => State.TIME_WAIT,

        (State.FIN_WAIT_1, Transition.RCV_ACK) => State.FIN_WAIT_2,

        (State.CLOSING, Transition.RCV_ACK) => State.TIME_WAIT,

        (State.FIN_WAIT_2, Transition.RCV_FIN) => State.TIME_WAIT,

        (State.TIME_WAIT, Transition.APP_TIMEOUT) => State.CLOSED,

        (State.CLOSE_WAIT, Transition.APP_CLOSE) => State.LAST_ACK,

        (State.LAST_ACK, Transition.RCV_ACK) => State.CLOSED,

        _ => State.ERROR

    };

​

    if (state == State.ERROR)

    {

        break;

    }

}

​

Console.WriteLine(state);

​

enum Transition

{

    APP_PASSIVE_OPEN,

    APP_ACTIVE_OPEN,

    RCV_SYN,

    APP_SEND,

    APP_CLOSE,

    RCV_ACK,

    RCV_SYN_ACK,

    RCV_FIN,

    RCV_FIN_ACK,

    APP_TIMEOUT

}

​

enum State

{

    ERROR,

    CLOSED,

    LISTEN,

    SYN_SENT,

    SYN_RCVD,

    ESTABLISHED,

    CLOSE_WAIT,

    LAST_ACK,

    FIN_WAIT_1,

    FIN_WAIT_2,

    TIME_WAIT,

    CLOSING

}