vrpn_Connection.h

#ifndef VRPN_CONNECTION_H
#define VRPN_CONNECTION_H

#include <stdio.h> // for NULL, sprintf

#include "vrpn_Configure.h" // for VRPN_API, VRPN_CALLBACK, etc
#include "vrpn_Shared.h"    // for SOCKET, timeval
#include "vrpn_Types.h"     // for vrpn_int32, vrpn_uint32, etc

#if !(defined(_WIN32) && defined(VRPN_USE_WINSOCK_SOCKETS))
#include <sys/select.h> // for fd_set
#endif

struct timeval;

// Don't complain about using sprintf() when using Visual Studio.
#ifdef _MSC_VER
#pragma warning(disable : 4995 4996)
#endif

#if defined(__ANDROID__)
#include <bitset>
#endif

/// This is the list of states that a connection can be in
/// (possible values for status).  doing_okay() returns VRPN_TRUE
/// for connections > BROKEN.
enum vrpn_ConnectionStatus {
    LISTEN = (1),
    CONNECTED = (0),
    COOKIE_PENDING = (-1),
    TRYING_TO_CONNECT = (-2),
    BROKEN = (-3),
    LOGGING = (-4)
};

class VRPN_API
    vrpn_File_Connection; // Forward declaration for get_File_Connection()

/// @brief This structure is what is passed to a vrpn_Connection message
/// callback.
///
/// It is used by objects, but not normally by user code.
struct vrpn_HANDLERPARAM {
    vrpn_int32 type;
    vrpn_int32 sender;
    struct timeval msg_time;
    vrpn_int32 payload_len;
    const char *buffer;
};

/// @brief Type of a message handler for vrpn_Connection messages.
typedef int(VRPN_CALLBACK *vrpn_MESSAGEHANDLER)(void *userdata,
                                                vrpn_HANDLERPARAM p);

/// @brief  Type of handler for filters on logfiles is the same as connection
/// handler
typedef vrpn_MESSAGEHANDLER vrpn_LOGFILTER;

/// VRPN buffers are aligned on 8 byte boundaries so that we can pack and
/// unpack doubles into them on architectures that cannot handle unaligned
/// access.
const unsigned vrpn_ALIGN = 8;

/// Types now have their storage dynamically allocated, so we can afford
/// to have large tables.  We need at least 150-200 for the microscope
/// project as of Jan 98, and will eventually need two to three times that
/// number.
/// @{
const int vrpn_CONNECTION_MAX_SENDERS = 2000;
const int vrpn_CONNECTION_MAX_TYPES = 2000;
/// @}

/// @brief vrpn_ANY_SENDER can be used to register callbacks on a given message
/// type from any sender.

const int vrpn_ANY_SENDER = -1;

/// @brief vrpn_ANY_TYPE can be used to register callbacks for any USER type of
/// message from a given sender.  System messages are handled separately.

const int vrpn_ANY_TYPE = -1;

/// @name Buffer lengths for TCP and UDP.
///
/// TCP is an arbitrary number that can be changed by the user
/// using vrpn_Connection::set_tcp_outbuf_size().
/// UDP is set based on Ethernet maximum transmission size;  trying
/// to send a message via UDP which is longer than the MTU of any
/// intervening physical network may cause untraceable failures,
/// so for now we do not expose any way to change the UDP output
/// buffer size.  (MTU = 1500 bytes, - 28 bytes of IP+UDP header)
/// @{

const int vrpn_CONNECTION_TCP_BUFLEN = 64000;
const int vrpn_CONNECTION_UDP_BUFLEN = 1472;
/// @}

/// @brief Number of endpoints that a server connection can have.  Arbitrary
/// limit.

const int vrpn_MAX_ENDPOINTS = 256;

/// @name System message types
/// @{
const vrpn_int32 vrpn_CONNECTION_SENDER_DESCRIPTION = (-1);
const vrpn_int32 vrpn_CONNECTION_TYPE_DESCRIPTION = (-2);
const vrpn_int32 vrpn_CONNECTION_UDP_DESCRIPTION = (-3);
const vrpn_int32 vrpn_CONNECTION_LOG_DESCRIPTION = (-4);
const vrpn_int32 vrpn_CONNECTION_DISCONNECT_MESSAGE = (-5);
/// @}

/// Classes of service for messages, specify multiple by ORing them together
/// Priority of satisfying these should go from the top down (RELIABLE will
/// override all others).
/// Most of these flags may be ignored, but RELIABLE is guaranteed
/// to be available.
/// @{

const vrpn_uint32 vrpn_CONNECTION_RELIABLE = (1 << 0);
const vrpn_uint32 vrpn_CONNECTION_FIXED_LATENCY = (1 << 1);
const vrpn_uint32 vrpn_CONNECTION_LOW_LATENCY = (1 << 2);
const vrpn_uint32 vrpn_CONNECTION_FIXED_THROUGHPUT = (1 << 3);
const vrpn_uint32 vrpn_CONNECTION_HIGH_THROUGHPUT = (1 << 4);

/// @}

/// @name What to log
/// @{
const long vrpn_LOG_NONE = (0);
const long vrpn_LOG_INCOMING = (1 << 0);
const long vrpn_LOG_OUTGOING = (1 << 1);
/// @}

// If defined, will filter out messages:  if the remote side hasn't
// registered a type, messages of that type won't be sent over the
// link.  WARNING:  auto-type-registration breaks this.
//#define vrpn_FILTER_MESSAGES

/// These are the strings that define the system-generated message
/// types that tell when connections are received and dropped.
/// @{
extern VRPN_API const char *vrpn_got_first_connection;
extern VRPN_API const char *vrpn_got_connection;
extern VRPN_API const char *vrpn_dropped_connection;
extern VRPN_API const char *vrpn_dropped_last_connection;
/// @}

/// @brief vrpn_CONTROL is the sender used for notification messages sent to the
/// user
/// from the local VRPN implementation (got_first_connection, etc.)
/// and for control messages sent by auxiliary services.  (Such as
/// class vrpn_Controller, which will be introduced in a future revision.)

extern VRPN_API const char *vrpn_CONTROL;

/// @brief Length of names within VRPN
typedef char cName[100];

/// Placed here so vrpn_FileConnection can use it too.
struct VRPN_API vrpn_LOGLIST {
    vrpn_HANDLERPARAM data;
    vrpn_LOGLIST *next;
    vrpn_LOGLIST *prev;
};

/// @todo HACK
/// These structs must be declared outside of vrpn_Connection
/// (although we'd like to make them protected/private members)
/// because aCC on PixelFlow doesn't handle nested classes correctly.
/// @{

/// @brief Description of a callback entry for a user type.
struct vrpnMsgCallbackEntry {
    vrpn_MESSAGEHANDLER handler; ///< Routine to call
    void *userdata;              ///< Passed along
    vrpn_int32 sender;           ///< Only if from sender
    vrpnMsgCallbackEntry *next;  ///< Next handler
};

struct vrpnLogFilterEntry {
    vrpn_LOGFILTER filter; ///< routine to call
    void *userdata;        ///< passed along
    vrpnLogFilterEntry *next;
};
/// @}

class VRPN_API vrpn_Connection;
class VRPN_API vrpn_Log;
class VRPN_API vrpn_TranslationTable;
class VRPN_API vrpn_TypeDispatcher;

/// @brief Encapsulation of the data and methods for a single generic connection
/// to take care of one part of many clients talking to a single server.
///
/// This will only be used from within the vrpn_Connection class;  it should
/// not be instantiated by users or devices.
/// Should not be visible!

class VRPN_API vrpn_Endpoint {

public:
    vrpn_Endpoint(vrpn_TypeDispatcher *dispatcher,
                  vrpn_int32 *connectedEndpointCounter);
    virtual ~vrpn_Endpoint(void);

    /// @name Accessors
    /// @{

    /// Returns the local mapping for the remote type (-1 if none).
    int local_type_id(vrpn_int32 remote_type) const;

    /// Returns the local mapping for the remote sender (-1 if none).
    int local_sender_id(vrpn_int32 remote_sender) const;

    virtual vrpn_bool doing_okay(void) const = 0;
    /// @}

    /// @name Manipulators
    /// @{

    void init(void);

    virtual int mainloop(timeval *timeout) = 0;

    /// Clear out the remote mapping list. This is done when a
    /// connection is dropped and we want to try and re-establish
    /// it.
    void clear_other_senders_and_types(void);

    /// A new local sender or type has been established; set
    /// the local type for it if the other side has declared it.
    /// Return 1 if the other side has one, 0 if not.
    int newLocalSender(const char *name, vrpn_int32 which);
    int newLocalType(const char *name, vrpn_int32 which);

    /// Adds a new remote type/sender and returns its index.
    /// Returns -1 on error.
    /// @{
    int newRemoteType(cName type_name, vrpn_int32 remote_id,
                      vrpn_int32 local_id);
    int newRemoteSender(cName sender_name, vrpn_int32 remote_id,
                        vrpn_int32 local_id);
    /// @}

    /// Pack a message that will be sent the next time mainloop() is called.
    /// Turn off the RELIABLE flag if you want low-latency (UDP) send.
    virtual int pack_message(vrpn_uint32 len, struct timeval time,
                             vrpn_int32 type, vrpn_int32 sender,
                             const char *buffer,
                             vrpn_uint32 class_of_service) = 0;

    /// send pending report, clear the buffer.
    /// This function was protected, now is public, so we can use it
    /// to send out intermediate results without calling mainloop
    virtual int send_pending_reports(void) = 0;

    int pack_log_description(void);
    ///< Packs the log description set by setup_new_connection().

    virtual int setup_new_connection(void) = 0;
    ///< Sends the magic cookie and other information to its
    ///< peer.  It is called by both the client and server setup routines.

    virtual void poll_for_cookie(const timeval *timeout = NULL) = 0;
    virtual int finish_new_connection_setup(void) = 0;

    virtual void drop_connection(void) = 0;
    ///< Should only be called by vrpn_Connection::drop_connection(),
    ///< since there's more housecleaning to do at that level.  I suppose
    ///< that argues against separating this function out.

    virtual void clearBuffers(void) = 0;
    ///< Empties out the TCP and UDP send buffers.
    ///< Needed by vrpn_FileConnection to get at {udp,tcp}NumOut.

    int pack_sender_description(vrpn_int32 which);
    ///< Packs a sender description over our socket.

    int pack_type_description(vrpn_int32 which);
    ///< Packs a type description.

    /// @}
    int status;

    /// @todo XXX These should be protected; making them so will lead to making
    ///    the code split the functions between Endpoint and Connection
    ///    protected:

    long d_remoteLogMode;     ///< Mode to put the remote logging in
    char *d_remoteInLogName;  ///< Name of the remote log file
    char *d_remoteOutLogName; ///< Name of the remote log file

    ///< Name of the remote host we are connected to.  This is kept for
    ///< informational purposes.  It is printed by the ceiling server,
    ///< for example.
    char rhostname[150];

    /// @name Logging
    ///
    /// TCH 19 April 00;  changed into two logs 16 Feb 01
    /// @{

    vrpn_Log *d_inLog;
    vrpn_Log *d_outLog;

    void setLogNames(const char *inName, const char *outName);
    int openLogs(void);
    /// @}

    /// @name Routines that handle system messages
    ///
    /// Visible so that vrpn_Connection can pass them to the Dispatcher
    /// @{
    static int VRPN_CALLBACK
    handle_sender_message(void *userdata, vrpn_HANDLERPARAM p);
    static int VRPN_CALLBACK
    handle_type_message(void *userdata, vrpn_HANDLERPARAM p);
    /// @}

    /// @name Routines to inform the endpoint of the connection of
    /// which it is a part.
    /// @{
    void setConnection(vrpn_Connection *conn) { d_parent = conn; }
    vrpn_Connection *getConnection() { return d_parent; }
    /// @}

protected:
    virtual int dispatch(vrpn_int32 type, vrpn_int32 sender, timeval time,
                         vrpn_uint32 payload_len, char *bufptr);

    int tryToMarshall(char *outbuf, vrpn_int32 &buflen, vrpn_int32 &numOut,
                      vrpn_uint32 len, timeval time, vrpn_int32 type,
                      vrpn_int32 sender, const char *buffer,
                      vrpn_uint32 classOfService);
    ///< Calls marshall_message();  if that fails, calls
    ///< send_pending_reports() and then marshalls again.
    ///< Returns the number of characters successfully marshalled.

    int marshall_message(char *outbuf, vrpn_uint32 outbuf_size,
                         vrpn_uint32 initial_out, vrpn_uint32 len,
                         struct timeval time, vrpn_int32 type,
                         vrpn_int32 sender, const char *buffer,
                         vrpn_uint32 sequenceNumber);

    // The senders and types we know about that have been described by
    // the other end of the connection.  Also, record the local mapping
    // for ones that have been described with the same name locally.
    // The arrays are indexed by the ID from the other side, and store
    // the name and local ID that corresponds to each.

    vrpn_TranslationTable *d_senders;
    vrpn_TranslationTable *d_types;

    vrpn_TypeDispatcher *d_dispatcher;
    vrpn_int32 *d_connectionCounter;

    vrpn_Connection *d_parent;
};

/// @brief Encapsulation of the data and methods for a single IP-based
/// connection
/// to take care of one part of many clients talking to a single server.
///
/// This will only be used from within the vrpn_Connection_IP class;  it should
/// not be instantiated by users or devices.
/// Should not be visible!

class VRPN_API vrpn_Endpoint_IP : public vrpn_Endpoint {

public:
    vrpn_Endpoint_IP(vrpn_TypeDispatcher *dispatcher,
                     vrpn_int32 *connectedEndpointCounter);
    virtual ~vrpn_Endpoint_IP(void);

    /// @name Accessors
    /// @{
    virtual vrpn_bool doing_okay(void) const;

    /// True if the UDP outbound is open, False if not.
    vrpn_bool outbound_udp_open(void) const;

    vrpn_int32 tcp_outbuf_size(void) const;
    vrpn_int32 udp_outbuf_size(void) const;
    /// @}

    /// @name Manipulators
    /// @{

    void init(void);

    int mainloop(timeval *timeout);

    /// @brief Pack a message that will be sent the next time mainloop() is
    /// called.
    ///
    /// Turn off the RELIABLE flag if you want low-latency (UDP) send.
    int pack_message(vrpn_uint32 len, struct timeval time, vrpn_int32 type,
                     vrpn_int32 sender, const char *buffer,
                     vrpn_uint32 class_of_service);

    /// @brief send pending report, clear the buffer.
    ///
    /// This function was protected, now is public, so we can use it
    /// to send out intermediate results without calling mainloop
    virtual int send_pending_reports(void);

    int pack_udp_description(int portno);

    int handle_tcp_messages(const timeval *timeout);
    int handle_udp_messages(const timeval *timeout);

    int connect_tcp_to(const char *msg);
    int connect_tcp_to(const char *addr, int port);
    ///< Connects d_tcpSocket to the specified address (msg = "IP port");
    ///< sets status to COOKIE_PENDING;  returns 0 on success, -1 on failure
    int connect_udp_to(const char *addr, int port);
    ///< Connects d_udpSocket to the specified address and port;
    ///< returns 0 on success, sets status to BROKEN and returns -1
    ///< on failure.

    vrpn_int32 set_tcp_outbuf_size(vrpn_int32 bytecount);

    int setup_new_connection(void);
    ///< Sends the magic cookie and other information to its
    ///< peer.  It is called by both the client and server setup routines.

    void poll_for_cookie(const timeval *timeout = NULL);
    int finish_new_connection_setup(void);

    void drop_connection(void);
    ///< Should only be called by vrpn_Connection::drop_connection(),
    ///< since there's more housecleaning to do at that level.  I suppose
    ///< that argues against separating this function out.

    void clearBuffers(void);
    ///< Empties out the TCP and UDP send buffers.
    ///< Needed by vrpn_FileConnection to get at {udp,tcp}NumOut.

    void setNICaddress(const char *);

    /// @todo XXX These should be protected; making them so will lead to making
    ///    the code split the functions between Endpoint and Connection
    ///    protected:

    SOCKET d_tcpSocket;

    /// This section deals with when a client connection is trying to
    /// establish (or re-establish) a connection with its server. It
    /// keeps track of what we need to know to make this happen.

    SOCKET d_tcpListenSocket;
    int d_tcpListenPort;
    ///< Socket and port that the client listens on
    ///< when lobbing datagrams at the server and
    ///< waiting for it to call back.

	/// Socket to use to lob UDP requests asking for the server to
	/// call us back.
	SOCKET d_udpLobSocket;

    char *d_remote_machine_name;    ///< Machine to call
    int d_remote_port_number;       ///< Port to connect to on remote machine
    timeval d_last_connect_attempt; ///< When the last UDP lob occurred

    vrpn_bool d_tcp_only;
    ///< For connections made through firewalls or NAT with the
    ///< tcp: URL, we do not want to allow the endpoints on either
    ///< end to open a UDP link to their counterparts.  If this is
    ///< the case, then this flag should be set to true.

protected:
    int getOneTCPMessage(int fd, char *buf, size_t buflen);
    int getOneUDPMessage(char *buf, size_t buflen);

    SOCKET d_udpOutboundSocket;
    SOCKET d_udpInboundSocket;
    ///< Inbound unreliable messages come here.
    ///< Need one for each due to different
    ///< clock synchronization for each; we
    ///< need to know which server each message is from.
    ///< @todo XXX Now that we don't need multiple clocks, can we collapse this?

    char *d_tcpOutbuf;
    char *d_udpOutbuf;
    vrpn_int32 d_tcpBuflen;
    vrpn_int32 d_udpBuflen;
    vrpn_int32 d_tcpNumOut;
    vrpn_int32 d_udpNumOut;

    vrpn_int32 d_tcpSequenceNumber;
    vrpn_int32 d_udpSequenceNumber;

    vrpn_float64
        d_tcpAlignedInbuf[vrpn_CONNECTION_TCP_BUFLEN / sizeof(vrpn_float64) +
                          1];
    vrpn_float64
        d_udpAlignedInbuf[vrpn_CONNECTION_UDP_BUFLEN / sizeof(vrpn_float64) +
                          1];
    char *d_tcpInbuf;
    char *d_udpInbuf;

    char *d_NICaddress;
};

/// @brief Generic connection class not specific to the transport mechanism.
///
/// It abstracts all of the common functions.  Specific implementations
/// for IP, MPI, and other transport mechanisms follow.
class VRPN_API vrpn_Connection {

protected:
    /// Constructor for server connection.  This cannot be called
    /// directly any more because vrpn_Connection is an abstract base
    /// class.  Call vrpn_create_server_connection() to make a server
    /// of arbitrary type based on a name.
    vrpn_Connection(const char *local_in_logfile_name,
                    const char *local_out_logfile_name,
                    vrpn_Endpoint_IP *(*epa)(vrpn_Connection *,
                                             vrpn_int32 *) = allocateEndpoint);

    /// Constructor for client connection.  This cannot be called
    /// directly because vrpn_Connection is an abstract base class.
    /// Call vrpn_get_connection_by_name() to create a client connection.
    vrpn_Connection(const char *local_in_logfile_name,
                    const char *local_out_logfile_name,
                    const char *remote_in_logfile_name,
                    const char *remote_out_logfile_name,
                    vrpn_Endpoint_IP *(*epa)(vrpn_Connection *,
                                             vrpn_int32 *) = allocateEndpoint);

public:
    virtual ~vrpn_Connection(void);

    /// Returns vrpn_true if the connection is okay, vrpn_false if not
    virtual vrpn_bool doing_okay(void) const;

    /// Returns vrpn_true if the connection has been established, vrpn_false if not
    /// (For a networkless connection, this is equivalent to doing_okay()).
    virtual vrpn_bool connected(void) const;

    /// This function returns the logfile names of this connection in
    /// the parameters.  It will allocate memory for the name of each
    /// log file in use.  If no logging of a particular type is happening,
    /// then *(X_Y_logname) will be set to NULL.
    /// IMPORTANT:  code calling this function is responsible for freeing
    /// the memory allocated for these strings.
    void get_log_names(char **local_in_logname, char **local_out_logname,
                       char **remote_in_logname, char **remote_out_logname);

    /// Call each time through program main loop to handle receiving any
    /// incoming messages and sending any packed messages.
    /// Returns -1 when connection dropped due to error, 0 otherwise.
    /// (only returns -1 once per connection drop).
    /// Optional argument is TOTAL time to block on select() calls;
    /// there may be multiple calls to select() per call to mainloop(),
    /// and this timeout will be divided evenly between them.
    virtual int mainloop(const struct timeval *timeout = NULL) = 0;

    /// Get a token to use for the string name of the sender or type.
    /// Remember to check for -1 meaning failure.
    virtual vrpn_int32 register_sender(const char *name);
    virtual vrpn_int32 register_message_type(const char *name);

    /// Set up (or remove) a handler for a message of a given type.
    /// Optionally, specify which sender to handle messages from.
    /// Handlers will be called during mainloop().
    /// Your handler should return 0 or a communication error is assumed
    /// and the connection will be shut down.
    virtual int register_handler(vrpn_int32 type, vrpn_MESSAGEHANDLER handler,
                                 void *userdata,
                                 vrpn_int32 sender = vrpn_ANY_SENDER);
    virtual int unregister_handler(vrpn_int32 type, vrpn_MESSAGEHANDLER handler,
                                   void *userdata,
                                   vrpn_int32 sender = vrpn_ANY_SENDER);

    /// Pack a message that will be sent the next time mainloop() is called.
    /// Turn off the RELIABLE flag if you want low-latency (UDP) send.
    virtual int pack_message(vrpn_uint32 len, struct timeval time,
                             vrpn_int32 type, vrpn_int32 sender,
                             const char *buffer, vrpn_uint32 class_of_service);

    /// send pending report, clear the buffer.
    /// This function was protected, now is public, so we can use it
    /// to send out intermediate results without calling mainloop
    virtual int send_pending_reports(void) = 0;

    /// Returns the time since the connection opened.
    /// Some subclasses may redefine time.
    virtual int time_since_connection_open(struct timeval *elapsed_time);

    /// returns the current time in the connection (since the epoch -- UTC
    /// time).
    virtual timeval get_time();

    /// Returns the name of the specified sender/type, or NULL
    /// if the parameter is invalid.  Only works for user
    /// messages (type >= 0).
    virtual const char *sender_name(vrpn_int32 sender);
    virtual const char *message_type_name(vrpn_int32 type);

    /// @brief Sets up a filter function for logging.
    /// Any user message to be logged is first passed to this function,
    /// and will only be logged if the function returns zero (XXX).
    /// NOTE:  this only affects local logging - remote logging
    /// is unfiltered!  Only user messages are filtered;  all system
    /// messages are logged.
    /// Returns nonzero on failure.
    virtual int register_log_filter(vrpn_LOGFILTER filter, void *userdata);

    /// Save any messages on any endpoints which have been logged so far.
    virtual int save_log_so_far();

    /// vrpn_File_Connection implements this as "return this" so it
    /// can be used to detect a File_Connection and get the pointer for it
    virtual vrpn_File_Connection *get_File_Connection(void);

    /// This function should be seldom used.  It is here for the case of
    /// the vrpn_Imager, whose servers do not follow "The VRPN Way" because
    /// they try to jam more data into the network than there is bandwidth
    /// to support it.  As a result, a client may call mainloop() on the
    /// connection and have it never return -- there is always more data
    /// in the network to read, so we never hand control back to the main
    /// program.  The reason for the name comes from an old U.S. cartoon
    /// called "The Jetsons".  In it, George Jetson is running on a
    /// treadmill when it goes out of control and starts spinning so fast
    /// that he can't even run fast enough to reach the controls and turn
    /// it off.  He cries out to his wife, "Jane!  Stop this crazy thing!"
    /// The parameter specifies a trigger: if more than the specified number
    /// of messages come in on a given input channel during one mainloop()
    /// call, the connection should stop looking for more messages.  NOTE:
    /// this does not guarantee that only this many messages will be received,
    /// only that the connection will stop looking for new ones on a given
    /// channel once that many have been received (for example, UDP channels
    /// will parse all the rest of the messages in a packet before stopping).
    /// A value of 0 turns off the limit, and will cause all incoming messages
    /// to be handled before returning.
    void Jane_stop_this_crazy_thing(vrpn_uint32 stop_looking_after)
    {
        d_stop_processing_messages_after = stop_looking_after;
    };
    vrpn_uint32 get_Jane_value(void)
    {
        return d_stop_processing_messages_after;
    };

protected:
    /// If this value is greater than zero, the connection should stop
    /// looking for new messages on a given endpoint after this many
    /// are found.
    vrpn_uint32 d_stop_processing_messages_after;

    int connectionStatus; ///< Status of the connection

    static vrpn_Endpoint_IP *allocateEndpoint(vrpn_Connection *,
                                              vrpn_int32 *connectedEC);
    ///< Redefining this and passing it to constructors
    ///< allows a subclass to use a different subclass of Endpoint.
    ///< It should do NOTHING but return an endpoint
    ///< of the appropriate class;  it may not access subclass data,
    ///< since it'll be called from a constructor

    /// Sockets used to talk to remote Connection(s)
    /// and other information needed on a per-connection basis
    vrpn_Endpoint_IP *d_endpoints[vrpn_MAX_ENDPOINTS];
    vrpn_int32 d_numEndpoints;

    vrpn_int32 d_numConnectedEndpoints;
    ///< We need to track the number of connected endpoints separately
    ///< to properly send out got-first-connection/dropped-last-connection
    ///< messages.  This value is *managed* by the Endpoints, but we
    ///< need exactly one copy per Connection, so it's on the Connection.

    /// @brief Routines that handle system messages
    /// @{
    static int VRPN_CALLBACK
    handle_log_message(void *userdata, vrpn_HANDLERPARAM p);
    static int VRPN_CALLBACK
    handle_disconnect_message(void *userdata, vrpn_HANDLERPARAM p);
    /// @}

    virtual void init(void); ///< Base initialization for all constructors.

    int delete_endpoint(int whichEndpoint);
    int compact_endpoints(void);

    virtual int pack_sender_description(vrpn_int32 which);
    ///< Send the sender description to ALL endpoints.

    virtual int pack_type_description(vrpn_int32 which);
    ///< Send the type description to ALL endpoints.

    virtual int do_callbacks_for(vrpn_int32 type, vrpn_int32 sender,
                                 struct timeval time, vrpn_uint32 len,
                                 const char *buffer);

    /// Returns message type ID, or -1 if unregistered
    int message_type_is_registered(const char *) const;

    /// Timekeeping - TCH 30 June 98
    timeval start_time;

    //
    /// Counting references to this connection.
public:
    void addReference();
    void removeReference();

private:
    int d_references;

    //
    /// Specify whether this connection should be deleted automatically when
    ///  it is no longer need (reference count reaches zero).
    /// For connections created by the VRPN code (as is done in
    ///  get_connection_by_name) these should be auto-deleted.
    ///  Connections created by user code should not be auto-deleted;
    ///  that is up to the user to decide when finished.
    /// By default, the constructor sets this to FALSE.
    /// VRPN code (or user code) can set this to TRUE if it wants the
    ///  connection to be deleted automatically when the last service on it
    ///  is deleted
public:
    void setAutoDeleteStatus(bool setvalue) { d_autoDeleteStatus = setvalue; }

private:
    bool d_autoDeleteStatus; ///< FALSE by default.

public:
    /// Derived classes need access to d_dispatcher in their
    /// allocateEndpoint() routine.  Several compilers won't give it to
    /// them, even if they do inherit publicly.  Until we figure that
    /// out, d_dispatcher needs to be public.

    vrpn_TypeDispatcher *d_dispatcher;

protected:
    int doSystemCallbacksFor(vrpn_HANDLERPARAM, void *);

    /// Server logging w. multiconnection - TCH July 00
    /// Use one "hidden" endpoint for outgoing logs (?),
    /// standard per-endpoint logs with augmented names for incoming.
    /// To make a hidden endpoint we create d_endpoints[0] and increment
    /// the d_numEndpoints, but DON'T pass it d_numConnectedEndpoints
    /// (although it should be safe to do so, since it should never truly
    /// become connected, but we might have to "fake" it to get it to log
    /// correctly).

    // vrpn_Endpoint * d_serverLogEndpoint;
    int d_serverLogCount;
    vrpn_int32 d_serverLogMode;
    char *d_serverLogName;

    vrpn_Endpoint_IP *(*d_endpointAllocator)(vrpn_Connection *, vrpn_int32 *);
    vrpn_bool d_updateEndpoint;

    virtual void updateEndpoints(void);
    ///< This function will be called on the mainloop() iteration
    ///< after *d_endpointAllocator is called, which lets subclasses
    ///< do initialization.  (They can't do so during allocateEndpoint
    ///< because it's called during the Connection constructor when
    ///< their constructors haven't executed yet.)
};

class VRPN_API vrpn_Connection_IP : public vrpn_Connection {

protected:
    /// Make a client connection.  To access this from user code,
    /// call vrpn_get_connection_by_name().
    ///   Create a connection -  if server_name is not a file: name,
    /// makes an SDI-like connection to the named remote server
    /// (otherwise functions as a non-networked messaging hub).
    /// Port less than zero forces default.
    ///   Currently, server_name is an extended URL that defaults
    /// to VRPN connections at the port, but can be file:: to read
    /// from a file.  Other extensions should maintain this, so
    /// that VRPN uses URLs to name things that are to be connected
    /// to.
    vrpn_Connection_IP(const char *server_name,
                       int port = vrpn_DEFAULT_LISTEN_PORT_NO,
                       const char *local_in_logfile_name = NULL,
                       const char *local_out_logfile_name = NULL,
                       const char *remote_in_logfile_name = NULL,
                       const char *remote_out_logfile_name = NULL,
                       const char *NIC_IPaddress = NULL,
                       vrpn_Endpoint_IP *(*epa)(
                           vrpn_Connection *, vrpn_int32 *) = allocateEndpoint);

public:
    /// Make a server that listens for client connections.
    /// DEPRECATED: Call vrpn_create_server_connection() with the
    /// NIC name and port number you want.
    vrpn_Connection_IP(
        unsigned short listen_port_no = vrpn_DEFAULT_LISTEN_PORT_NO,
        const char *local_in_logfile_name = NULL,
        const char *local_out_logfile_name = NULL,
        const char *NIC_IPaddress = NULL,
        vrpn_Endpoint_IP *(*epa)(vrpn_Connection *,
                                 vrpn_int32 *) = allocateEndpoint);

    virtual ~vrpn_Connection_IP(void);

    /// This is similar to check connection except that it can be
    /// used to receive requests from before a server starts up
    virtual int connect_to_client(const char *machine, int port);

    /// Call each time through program main loop to handle receiving any
    /// incoming messages and sending any packed messages.
    /// Returns -1 when connection dropped due to error, 0 otherwise.
    /// (only returns -1 once per connection drop).
    /// Optional argument is TOTAL time to block on select() calls;
    /// there may be multiple calls to select() per call to mainloop(),
    /// and this timeout will be divided evenly between them.
    virtual int mainloop(const struct timeval *timeout = NULL);

protected:
    /// If this value is greater than zero, the connection should stop
    /// looking for new messages on a given endpoint after this many
    /// are found.
    vrpn_uint32 d_stop_processing_messages_after;

protected:
    friend VRPN_API vrpn_Connection *vrpn_get_connection_by_name(
        const char *cname, const char *local_in_logfile_name,
        const char *local_out_logfile_name, const char *remote_in_logfile_name,
        const char *remote_out_logfile_name, const char *NIC_IPaddress,
        bool force_connection);
    friend VRPN_API vrpn_Connection *
    vrpn_create_server_connection(const char *cname,
                                  const char *local_in_logfile_name,
                                  const char *local_out_logfile_name);

/// @name Only used for a vrpn_Connection that awaits incoming connections
/// @{
    SOCKET listen_udp_sock; ///< UDP Connect requests come here
    SOCKET listen_tcp_sock; ///< TCP Connection requests come here
    /// @}

    /// Routines that handle system messages
    static int VRPN_CALLBACK
    handle_UDP_message(void *userdata, vrpn_HANDLERPARAM p);

    /// @brief Called by all constructors
    virtual void init(void);

    /// @brief send pending report, clear the buffer.
    ///
    /// This function was protected, now is public, so we can use it
    /// to send out intermediate results without calling mainloop
    virtual int send_pending_reports(void);

    //// This is called by a server-side process to see if there have
    //// been any UDP packets come in asking for a connection. If there
    //// are, it connects the TCP port and then calls handle_connection().
    virtual void
    server_check_for_incoming_connections(const struct timeval *timeout = NULL);

    /// This routine is called by a server-side connection when a
    /// new connection has just been established, and the tcp port
    /// has been connected to it.
    virtual void handle_connection(int whichEndpoint);

    virtual void drop_connection(int whichEndpoint);

    char *d_NIC_IP;
};

/// @brief Constructor for a Loopback connection that will basically just
/// pass messages between objects that are connected to it.  It offers no
/// external connections, via IP or any other mechanism.  It is useful
/// if you want to make the client and server in the same connection and
/// you don't need to have anything else connect.

class VRPN_API vrpn_Connection_Loopback : public vrpn_Connection {

protected:
    /// Make a client connection.  To access this from user code,
    /// call vrpn_create_server_connection() with a service name
    /// of 'loopback:'.
    /// For now, we don't enable logging on a Loopback connection.
    vrpn_Connection_Loopback();
public:
    virtual ~vrpn_Connection_Loopback(void);

    /// Call each time through program main loop to handle receiving any
    /// incoming messages and sending any packed messages.
    /// Returns -1 on error, 0 otherwise.
    /// Optional argument is TOTAL time to block on select() calls;
    /// there may be multiple calls to select() per call to mainloop(),
    /// and this timeout will be divided evenly between them.
    virtual int mainloop(const struct timeval *timeout = NULL);

    /// Returns vrpn_true if the connection is okay, vrpn_false if not
    virtual vrpn_bool doing_okay(void) const { return vrpn_true; }

    /// Returns vrpn_true if the connection has been established, vrpn_false if not
    /// (For a networkless connection, this is equivalent to doing_okay()).
    virtual vrpn_bool connected(void) const { return vrpn_true; }

protected:
    friend VRPN_API vrpn_Connection *
    vrpn_create_server_connection(const char *cname,
                                  const char *local_in_logfile_name,
                                  const char *local_out_logfile_name);

    /// @brief send pending report, clear the buffer.
    ///
    /// This function was protected, now is public, so we can use it
    /// to send out intermediate results without calling mainloop
    virtual int send_pending_reports(void) {return 0;}
};

/// @brief Create a client connection of arbitrary type (VRPN UDP/TCP, TCP,
/// File, Loopback, MPI).
///
/// WARNING:  May not be thread safe.
/// If no IP address for the NIC to use is specified, uses the default
/// NIC.  If the force_reopen flag is set, a new connection will be
/// made even if there was already one to that server.
/// When done with the object, call removeReference() on it (which will
/// delete it if there are no other references).
VRPN_API vrpn_Connection *vrpn_get_connection_by_name(
    const char *cname, const char *local_in_logfile_name = NULL,
    const char *local_out_logfile_name = NULL,
    const char *remote_in_logfile_name = NULL,
    const char *remote_out_logfile_name = NULL,
    const char *NIC_IPaddress = NULL, bool force_reopen = false);

/// @brief Create a server connection of arbitrary type (VRPN UDP/TCP,
/// TCP, File, Loopback, MPI).
///
/// Returns NULL if the name is not understood or the connection cannot
/// be created.
/// WARNING:  May not be thread safe.
/// To create a VRPN TCP/UDP server, use a name like:
///    vrpn:machine_name_or_ip:port
///    machine_name_or_ip:port
///    machine_name_or_ip
///    :port       (This port on any network card.)
/// To create an MPI server, use a name like:
///    mpi:MPI_COMM_WORLD
///    mpi:comm_number
/// When done with the object, call removeReference() on it (which will
/// delete it if there are no other references).
VRPN_API vrpn_Connection *
vrpn_create_server_connection(const char *cname,
                              const char *local_in_logfile_name = NULL,
                              const char *local_out_logfile_name = NULL);

/// Lets you make one with the default settings, or just ask for a specific
/// port number on the default NIC on this machine.  This matches the
/// signature on the old constructor to make it easier to port existing
/// servers.
inline VRPN_API vrpn_Connection *
vrpn_create_server_connection(int port = vrpn_DEFAULT_LISTEN_PORT_NO,
                              const char *local_in_logfile_name = NULL,
                              const char *local_out_logfile_name = NULL,
                              const char *NIC_NAME = NULL)
{
    char name[256];
    if (NIC_NAME == NULL) {
        sprintf(name, ":%d", port);
    }
    else {
        sprintf(name, "%s:%d", NIC_NAME, port);
    }
    return vrpn_create_server_connection(name, local_in_logfile_name,
                                         local_out_logfile_name);
}

/// @name Utility routines to parse names (<service>@<location specifier>)
/// Both return new char [], and it is the caller's responsibility
/// to delete this memory!
/// @{
VRPN_API char *vrpn_copy_service_name(const char *fullname);
VRPN_API char *vrpn_copy_service_location(const char *fullname);
/// @}

/// @brief Utility routines to parse file specifiers FROM service locations
///
///   file:<filename>
///
///   file://<hostname>/<filename>
///
///   file:///<filename>
VRPN_API char *vrpn_copy_file_name(const char *filespecifier);

/// @name Utility routines to parse host specifiers FROM service locations
///
///   <hostname>
///
///   <hostname>:<port number>
///
///   x-vrpn://<hostname>
///
///   x-vrpn://<hostname>:<port number>
///
///   x-vrsh://<hostname>/<server program>,<comma-separated server arguments>
///
/// The caller is responsible for calling delete [] on the returned character
/// pointer if it is not NULL.
/// @{
VRPN_API char *vrpn_copy_machine_name(const char *hostspecifier);
VRPN_API int vrpn_get_port_number(const char *hostspecifier);
VRPN_API char *vrpn_copy_rsh_program(const char *hostspecifier);
VRPN_API char *vrpn_copy_rsh_arguments(const char *hostspecifier);
/// @}

/// @brief Utility routine to rename the service name of a given host specifier.
char *vrpn_set_service_name(const char *specifier, const char *newServiceName);

/// Checks the buffer to see if it is a valid VRPN header cookie.
/// Returns -1 on total mismatch,
/// 1 on minor version mismatch or other acceptable difference,
/// and 0 on exact match.
/// @{
VRPN_API int check_vrpn_cookie(const char *buffer);
VRPN_API int check_vrpn_file_cookie(const char *buffer);
/// @}

/// @brief Returns the size of the magic cookie buffer, plus any alignment
/// overhead.
VRPN_API size_t vrpn_cookie_size(void);

VRPN_API int write_vrpn_cookie(char *buffer, size_t length,
                               long remote_log_mode);

/// @name Utility routines for reading from and writing to sockets/file
/// descriptors
/// @{
#ifndef VRPN_USE_WINSOCK_SOCKETS
int VRPN_API
vrpn_noint_block_write(int outfile, const char buffer[], size_t length);
int VRPN_API vrpn_noint_block_read(int infile, char buffer[], size_t length);
int VRPN_API vrpn_noint_select(int width, fd_set *readfds, fd_set *writefds,
                               fd_set *exceptfds, struct timeval *timeout);
#else  /* winsock sockets */
int VRPN_API
vrpn_noint_block_write(SOCKET outsock, char *buffer, size_t length);
int VRPN_API vrpn_noint_block_read(SOCKET insock, char *buffer, size_t length);
#endif /* VRPN_USE_WINSOCK_SOCKETS */
       /// @}

/**
 * @brief Singleton class that keeps track of all known VRPN connections
 * and makes sure they're deleted on shutdown.
 *
 * We make it static to guarantee that the destructor is called
 * on program close so that the destructors of all the vrpn_Connections
 * that have been allocated are called so that all open logs are flushed
 * to disk.  Each connection should add itself to this list in its
 * constructor and should remove itself from this list in its
 * destructor.
 */

//      This section holds data structures and functions to open
// connections by name.
//      The intention of this section is that it can open connections for
// objects that are in different libraries (trackers, buttons and sound),
// even if they all refer to the same connection.

class VRPN_API vrpn_ConnectionManager {

public:
    ~vrpn_ConnectionManager(void);

    /// @brief The only way to get access to an instance of this class.
    /// Guarantees that there is only one, global object.
    /// Also guarantees that it will be constructed the first time
    /// this function is called, and (hopefully?) destructed when
    /// the program terminates.
    static vrpn_ConnectionManager &instance(void);

    /// NB implementation is not particularly efficient;  we expect
    /// to have O(10) connections, not O(1000).
    /// @{
    void addConnection(vrpn_Connection *, const char *name);
    void deleteConnection(vrpn_Connection *);
    /// @}

    /// Searches through d_kcList but NOT d_anonList
    /// (Connections constructed with no name)
    vrpn_Connection *getByName(const char *name);

private:
    struct knownConnection {
        char name[1000];
        vrpn_Connection *connection;
        knownConnection *next;
    };

    /// @brief named connections
    knownConnection *d_kcList;

    /// @brief unnamed (server) connections
    knownConnection *d_anonList;

    vrpn_ConnectionManager(void);

    // @brief copy constructor undefined to prevent instantiations
    vrpn_ConnectionManager(const vrpn_ConnectionManager &);

    static void deleteConnection(vrpn_Connection *, knownConnection **);
};

#endif // VRPN_CONNECTION_H