WiFiServer.h

/*
    WiFiServer.h - Library for Arduino Wifi shield.
    Copyright (c) 2011-2014 Arduino LLC.  All right reserved.

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Modified by Ivan Grokhotkov, December 2014 - esp8266 support
*/

#pragma once

#include <wl_definitions.h>
struct tcp_pcb;

#include <Server.h>
#include <IPAddress.h>
#include <lwip/err.h>

// lwIP-v2 backlog facility allows to keep memory safe by limiting the
// maximum number of incoming *pending clients*.  Default number of possibly
// simultaneously pending clients is defined in WiFiServer.cpp
// (MAX_PENDING_CLIENTS_PER_PORT=5).  User can override it at runtime from
// sketch:
//      WiFiServer::begin(port, max-simultaneous-pending-clients);
//
// An "incoming pending" client is a new incoming TCP connection trying to
// reach the TCP server.  It is "pending" until lwIP acknowledges it and
// "accepted / no more pending" when user calls WiFiServer::available().
//
// Before the backlog feature or with lwIP-v1.4, there was no pending
// connections: They were immediately accepted and filling RAM.
//
// Several pending clients can appear during the time when one client is
// served by a long not-async service like ESP8266WebServer.  During that
// time WiFiServer::available() cannot be called.
//
// Note: This *does not limit* the number of *simultaneously accepted
//       clients*.  Such limit management is left to the user.
//
// Thus, when the maximum number of pending connections is reached, new
// connections are delayed.
// By "delayed", it is meant that WiFiServer(lwIP) will not answer to the
// SYN packet until there is room for a new one: The TCP server on that port
// will be mute.  The TCP client will regularly try to connect until success
// or a timeout occurs (72s on windows).
//
// When user calls WiFiServer::available(), the tcp server stops muting and
// answers to newcomers (until the "backlog" pending list is full again).

class ClientContext;
class WiFiClient;

class WiFiServer {
    // Secure server needs access to all the private entries here
protected:
    uint16_t _port;
    IPAddress _addr;
    tcp_pcb* _listen_pcb = nullptr;

    ClientContext* _unclaimed = nullptr;
    ClientContext* _discarded = nullptr;
    enum { _ndDefault, _ndFalse, _ndTrue } _noDelay = _ndDefault;

public:
    WiFiServer(const IPAddress& addr, uint16_t port);
    WiFiServer(uint16_t port = 23);
    virtual ~WiFiServer() {}
    WiFiClient accept(); // https://www.arduino.cc/en/Reference/EthernetServerAccept
    WiFiClient available(uint8_t* status = nullptr) __attribute__((deprecated("Use accept().")));

    bool hasClient();
    // hasClientData():
    // returns the amount of data available from the first client
    // or 0 if there is none
    size_t hasClientData();
    // hasMaxPendingClients():
    // returns true if the queue of pending clients is full
    bool hasMaxPendingClients();
    void begin();
    void begin(uint16_t port);
    void begin(uint16_t port, uint8_t backlog);
    void setNoDelay(bool nodelay);
    bool getNoDelay();
    uint8_t status();
    uint16_t port() const;
    void end();
    void close();
    void stop();
    explicit operator bool();

    using ClientType = WiFiClient;

protected:
    err_t  _accept(tcp_pcb* newpcb, err_t err);
    void   _discard(ClientContext* client);

    static err_t _s_accept(void *arg, tcp_pcb* newpcb, err_t err);
    static void _s_discard(void* server, ClientContext* ctx);
};