MCast Class

Properties   Methods   Events   Config Settings   Errors  

The MCast class is used to multicast User Datagram Protocol (UDP) datagrams to multicast-capable hosts in multicast-capable subnets. It can act both as a client and a server and can communicate with any number of hosts simultaneously, as well as generate and receive broadcast packets.

Syntax

MCast

Remarks

The MCast class is very similar to UDP, except for some additional properties that provide support for multicast datagrams. To send datagrams to a multicast group, simply assign the address of the group to RemoteHost. To receive datagrams from one or more groups, assign the group addresses to MulticastGroup one by one (after the class is activated). TimeToLive allows you to specify how many subnets a packet should be allowed to receive. ReceiveInterface and SendInterface allow you to select the network interface for multicast operations.

The class is activated/deactivated through the Active property. This property enables or disables sends or receives. The data can be sent in the same way as UDP, by calling the Send method with a Text parameter. The destination is specified using the RemoteHost and RemotePort properties. Inbound data are received through the DataIn event.

Property List

The following is the full list of the properties of the class with short descriptions. Click on the links for further details.

Method List

The following is the full list of the methods of the class with short descriptions. Click on the links for further details.

Event List

The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.

Config Settings

The following is a list of config settings for the class with short descriptions. Click on the links for further details.

AcceptData Property (MCast Class)

This property indicates whether data reception is currently enabled.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetAcceptData();

Unicode (Windows)
BOOL GetAcceptData();

int ipworks_mcast_getacceptdata(void* lpObj);

bool GetAcceptData();

Default Value

TRUE

Remarks

This property indicates whether data reception is currently enabled. When false, data reception is disabled and the DataIn event will not fire. Use the PauseData and ProcessData methods to pause and resume data reception.

This property is read-only and not available at design time.

Data Type

Boolean

Active Property (MCast Class)

This property indicates whether the class is active.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetActive();

Unicode (Windows)
BOOL GetActive();

int ipworks_mcast_getactive(void* lpObj);

bool GetActive();

Default Value

FALSE

Remarks

This property indicates whether the class is currently active and can send or receive data. Use the Activate and Deactivate methods to control whether the class is active.

This property is read-only and not available at design time.

Data Type

Boolean

LocalHost Property (MCast Class)

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetLocalHost();
int SetLocalHost(const char* lpszLocalHost);

Unicode (Windows)
LPWSTR GetLocalHost();
INT SetLocalHost(LPCWSTR lpszLocalHost);

char* ipworks_mcast_getlocalhost(void* lpObj);
int ipworks_mcast_setlocalhost(void* lpObj, const char* lpszLocalHost);

QString GetLocalHost();
int SetLocalHost(QString qsLocalHost);

Default Value

""

Remarks

This property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multihomed hosts (machines with more than one IP interface) setting LocalHost to the IP address of an interface will make the class initiate connections (or accept in the case of server classs) only through that interface. It is recommended to provide an IP address rather than a hostname when setting this property to ensure the desired interface is used.

If the class is connected, the LocalHost property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multihomed hosts (machines with more than one IP interface).

Note: LocalHost is not persistent. You must always set it in code, and never in the property window.

Data Type

String

LocalPort Property (MCast Class)

This property includes the User Datagram Protocol (UDP) port in the local host where MCast binds.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetLocalPort();
int SetLocalPort(int iLocalPort);

Unicode (Windows)
INT GetLocalPort();
INT SetLocalPort(INT iLocalPort);

int ipworks_mcast_getlocalport(void* lpObj);
int ipworks_mcast_setlocalport(void* lpObj, int iLocalPort);

int GetLocalPort();
int SetLocalPort(int iLocalPort);

Default Value

0

Remarks

This property must be set before MCast is activated (Active is set to True). It instructs the class to bind to a specific port (or communication endpoint) on the local machine.

Setting it to 0 (default) enables the system to choose a port at random. The chosen port will be shown by this property after the connection is established.

This property cannot be changed once the class is Active. Any attempt to set this property when the class is Active will generate an error.

This property is useful when trying to send data to services that require a trusted port on the client side.

Data Type

Integer

Loopback Property (MCast Class)

This property enables or disables loopback of data sent to the multicast group.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetLoopback();
int SetLoopback(int bLoopback);

Unicode (Windows)
BOOL GetLoopback();
INT SetLoopback(BOOL bLoopback);

int ipworks_mcast_getloopback(void* lpObj);
int ipworks_mcast_setloopback(void* lpObj, int bLoopback);

bool GetLoopback();
int SetLoopback(bool bLoopback);

Default Value

TRUE

Remarks

This property enables or disables loopback of data sent to the multicast group. Setting this property to False disables loopback of data sent through the class (normally loopback is enabled). This property is directly related to the IP_MULTICAST_LOOP socket option.

This property is not available at design time.

Data Type

Boolean

MulticastGroup Property (MCast Class)

This property includes the multicast group to join or leave.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetMulticastGroup();
int SetMulticastGroup(const char* lpszMulticastGroup);

Unicode (Windows)
LPWSTR GetMulticastGroup();
INT SetMulticastGroup(LPCWSTR lpszMulticastGroup);

char* ipworks_mcast_getmulticastgroup(void* lpObj);
int ipworks_mcast_setmulticastgroup(void* lpObj, const char* lpszMulticastGroup);

QString GetMulticastGroup();
int SetMulticastGroup(QString qsMulticastGroup);

Default Value

""

Remarks

This property contains the multicast group to join or leave. Multicast groups are joined by assigning values to this property after the class is activated. More than one group may be joined at the same time. To define which interface to use, the ReceiveInterface property is used.

Determining whether a group is left or joined is done by setting the first letter of MulticastGroup to "-" or "+". The default operation is join.

To remove the class from a multicast group once it is joined, simply assign this groupname (address) to MulticastGroup prefixed by a minus sign "-".

Example. Joining/Leaving Groups:

MCastControl.Active = true MCastControl.MulticastGroup = "+231.31.31.31" MCastControl.MulticastGroup = "+232.32.32.32" MCastControl.MulticastGroup = "-232.32.32.32" MCastControl.MulticastGroup = "-231.31.31.31"

Data Type

String

ReceiveInterface Property (MCast Class)

This property includes the interface with which to receive multicast packets. If empty, the default is used.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetReceiveInterface();
int SetReceiveInterface(const char* lpszReceiveInterface);

Unicode (Windows)
LPWSTR GetReceiveInterface();
INT SetReceiveInterface(LPCWSTR lpszReceiveInterface);

char* ipworks_mcast_getreceiveinterface(void* lpObj);
int ipworks_mcast_setreceiveinterface(void* lpObj, const char* lpszReceiveInterface);

QString GetReceiveInterface();
int SetReceiveInterface(QString qsReceiveInterface);

Default Value

""

Remarks

This property is useful when there is more than one network interface, and the one used for receiving multicast datagrams is not the default. If you wish to set an interface other than the system default, provide the IP address of the interface to be set.

This property is used along with the MulticastGroup property to join one or more multicast groups. The joining is done after the class is activated by assigning proper values to MulticastGroup.

This property is not available at design time.

Data Type

String

RemoteHost Property (MCast Class)

This property includes the address of the remote host (multicast group).

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetRemoteHost();
int SetRemoteHost(const char* lpszRemoteHost);

Unicode (Windows)
LPWSTR GetRemoteHost();
INT SetRemoteHost(LPCWSTR lpszRemoteHost);

char* ipworks_mcast_getremotehost(void* lpObj);
int ipworks_mcast_setremotehost(void* lpObj, const char* lpszRemoteHost);

QString GetRemoteHost();
int SetRemoteHost(QString qsRemoteHost);

Default Value

""

Remarks

This property contains the address of the remote host (multicast group). To send a multicast datagram, specify a RemoteHost value in the range of 224.0.0.0 to 239.255.255.255. These addresses are reserved as multicast addresses by IP.

Data Type

String

RemotePort Property (MCast Class)

This property includes the User Datagram Protocol (UDP) port on the remote host.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetRemotePort();
int SetRemotePort(int iRemotePort);

Unicode (Windows)
INT GetRemotePort();
INT SetRemotePort(INT iRemotePort);

int ipworks_mcast_getremoteport(void* lpObj);
int ipworks_mcast_setremoteport(void* lpObj, int iRemotePort);

int GetRemotePort();
int SetRemotePort(int iRemotePort);

Default Value

0

Remarks

This property contains the UDP port on the RemoteHost to send UDP datagrams to.

A valid port number (i.e., a value between 1 and 65535) is required.

Data Type

Integer

SendInterface Property (MCast Class)

This property includes the interface from which multicast packets are sent. If empty, the default is used.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* GetSendInterface();
int SetSendInterface(const char* lpszSendInterface);

Unicode (Windows)
LPWSTR GetSendInterface();
INT SetSendInterface(LPCWSTR lpszSendInterface);

char* ipworks_mcast_getsendinterface(void* lpObj);
int ipworks_mcast_setsendinterface(void* lpObj, const char* lpszSendInterface);

QString GetSendInterface();
int SetSendInterface(QString qsSendInterface);

Default Value

""

Remarks

This property is useful when there is more than one network interface, and the one used for sending multicast datagrams is not the default. If you wish to set an interface other than the system default, provide the IP address of the interface to be set.

This property is not available at design time.

Data Type

String

TimeToLive Property (MCast Class)

This property includes the maximum number of subnets that a multicast datagram can traverse.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetTimeToLive();
int SetTimeToLive(int iTimeToLive);

Unicode (Windows)
INT GetTimeToLive();
INT SetTimeToLive(INT iTimeToLive);

int ipworks_mcast_gettimetolive(void* lpObj);
int ipworks_mcast_settimetolive(void* lpObj, int iTimeToLive);

int GetTimeToLive();
int SetTimeToLive(int iTimeToLive);

Default Value

7

Remarks

This property contains the maximum number of subnets that a multicast datagram can traverse. The default value for this property is 7. This is an arbitrary value. You need to specify a value suitable for your application.

Multicast datagrams with this property set to 0 are not transmitted on any subnetwork. Multicast datagrams with this property set to 1 are delivered only on the local network. Multicast datagrams with this property set to greater than 1 may be delivered to more than one subnetwork if one or more multicast routers are attached to the first-hop subnetwork.

A multicast router does not forward multicast datagrams with destination addresses between 224.0.0.0 and 224.0.0.255, inclusive, regardless of their TimeToLive. This particular range of addresses is reserved for the use of routing protocols and other low-level topology discovery or maintenance protocols, such as gateway discovery and group membership reporting.

Data Type

Integer

Activate Method (MCast Class)

This method enables sending and receiving of data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Activate();

Unicode (Windows)
INT Activate();

int ipworks_mcast_activate(void* lpObj);

int Activate();

Remarks

This method enables sending and receiving of data. When called, the component will create a communication endpoint (socket) that can be used for sending and receiving User Datagram Protocol (UDP) datagrams.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Config Method (MCast Class)

Sets or retrieves a configuration setting.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
char* Config(const char* lpszConfigurationString);

Unicode (Windows)
LPWSTR Config(LPCWSTR lpszConfigurationString);

char* ipworks_mcast_config(void* lpObj, const char* lpszConfigurationString);

QString Config(const QString& qsConfigurationString);

Remarks

Config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

Error Handling (C++)

This method returns a String value; after it returns, call the GetLastErrorCode() method to obtain its result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.

Deactivate Method (MCast Class)

This method disables sending and receiving of data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Deactivate();

Unicode (Windows)
INT Deactivate();

int ipworks_mcast_deactivate(void* lpObj);

int Deactivate();

Remarks

This method disables sending and receiving of data. When called, the component will destroy the existing socket and disable data communications.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

DoEvents Method (MCast Class)

This method processes events from the internal message queue.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int DoEvents();

Unicode (Windows)
INT DoEvents();

int ipworks_mcast_doevents(void* lpObj);

int DoEvents();

Remarks

When DoEvents is called, the class processes any available events. If no events are available, it waits for a preset period of time, and then returns.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

PauseData Method (MCast Class)

This method pauses data reception.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int PauseData();

Unicode (Windows)
INT PauseData();

int ipworks_mcast_pausedata(void* lpObj);

int PauseData();

Remarks

This method pauses data reception when called. While data reception is paused, the DataIn event will not fire. Call ProcessData to reenable data reception.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

ProcessData Method (MCast Class)

This method reenables data reception after a call to PauseData .

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int ProcessData();

Unicode (Windows)
INT ProcessData();

int ipworks_mcast_processdata(void* lpObj);

int ProcessData();

Remarks

This method reenables data reception after a previous call to PauseData. When PauseData is called, the DataIn event will not fire. To reenable data reception and allow DataIn to fire, call this method.

Note: This method is used only after previously calling PauseData. It does not need to be called to process incoming data by default.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Reset Method (MCast Class)

This method resets the class.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Reset();

Unicode (Windows)
INT Reset();

int ipworks_mcast_reset(void* lpObj);

int Reset();

Remarks

This method will reset the class's properties to their default values.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

ResolveRemoteHost Method (MCast Class)

This method resolves the hostname in RemoteHost to an IP address.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int ResolveRemoteHost();

Unicode (Windows)
INT ResolveRemoteHost();

int ipworks_mcast_resolveremotehost(void* lpObj);

int ResolveRemoteHost();

Remarks

This method resolves the hostname specified by RemoteHost to an IP address. The resolved value is available in the RemoteHost property after this method returns.

In most cases, calling this method is not necessary; the class will resolve the hostname automatically when needed. If DelayHostResolution is true, this method may be called to manually resolve RemoteHost, if desired.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

Send Method (MCast Class)

This method sends data to the remote host.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Send(const char* lpText, int lenText);

Unicode (Windows)
INT Send(LPCSTR lpText, INT lenText);

int ipworks_mcast_send(void* lpObj, const char* lpText, int lenText);

int Send(QByteArray qbaText);

Remarks

This method sends data to the remote host.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

SendBytes Method (MCast Class)

This method sends data to the remote host.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int SendBytes(const char* lpData, int lenData);

Unicode (Windows)
INT SendBytes(LPCSTR lpData, INT lenData);

int ipworks_mcast_sendbytes(void* lpObj, const char* lpData, int lenData);

int SendBytes(QByteArray qbaData);

Remarks

This method sends data to the remote host. Calling this method is equivalent to calling the SendBytes/SendText method.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

SendText Method (MCast Class)

This method sends data to the remote host.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int SendText(const char* lpszText);

Unicode (Windows)
INT SendText(LPCWSTR lpszText);

int ipworks_mcast_sendtext(void* lpObj, const char* lpszText);

int SendText(const QString& qsText);

Remarks

This method sends data to the remote host. Calling this method is equivalent to calling the SendBytes/SendText method.

Error Handling (C++)

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)

DataIn Event (MCast Class)

This event is fired when data are received.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireDataIn(MCastDataInEventParams *e);

typedef struct {
  const char *Datagram;
  int lenDatagram;
  const char *SourceAddress;
  int SourcePort;
  int reserved;
} MCastDataInEventParams;


Unicode (Windows)
virtual INT FireDataIn(MCastDataInEventParams *e);

typedef struct {
  LPCSTR Datagram;
  INT lenDatagram;
  LPCWSTR SourceAddress;
  INT SourcePort;
  INT reserved;
} MCastDataInEventParams;

#define EID_MCAST_DATAIN 1

virtual INT IPWORKS_CALL FireDataIn(LPSTR &lpDatagram, INT &lenDatagram, LPSTR &lpszSourceAddress, INT &iSourcePort);

class MCastDataInEventParams {
public:
  const QByteArray &Datagram();

  const QString &SourceAddress();

  int SourcePort();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void DataIn(MCastDataInEventParams *e);

// Or, subclass MCast and override this emitter function.
virtual int FireDataIn(MCastDataInEventParams *e) {...}

Remarks

The DataIn event is fired every time a new datagram is received.

Datagram contains the packet as sent by the remote host.

SourceAddress contains the IP number (Internet address) of the remote host, and SourcePort contains the port from which the packet originated.

Note: Events are not re-entrant. Performing time-consuming operations within this event will prevent it from firing again in a timely manner and may affect overall performance.

Error Event (MCast Class)

Fired when information is available about errors during data delivery.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireError(MCastErrorEventParams *e);

typedef struct {
  int ErrorCode;
  const char *Description;
  int reserved;
} MCastErrorEventParams;


Unicode (Windows)
virtual INT FireError(MCastErrorEventParams *e);

typedef struct {
  INT ErrorCode;
  LPCWSTR Description;
  INT reserved;
} MCastErrorEventParams;

#define EID_MCAST_ERROR 2

virtual INT IPWORKS_CALL FireError(INT &iErrorCode, LPSTR &lpszDescription);

class MCastErrorEventParams {
public:
  int ErrorCode();

  const QString &Description();

  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void Error(MCastErrorEventParams *e);

// Or, subclass MCast and override this emitter function.
virtual int FireError(MCastErrorEventParams *e) {...}

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the class fails with an error.

The ErrorCode parameter contains an error code, and the Description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

ReadyToSend Event (MCast Class)

This event is fired when the class is ready to send data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
virtual int FireReadyToSend(MCastReadyToSendEventParams *e);

typedef struct {
  int reserved;
} MCastReadyToSendEventParams;


Unicode (Windows)
virtual INT FireReadyToSend(MCastReadyToSendEventParams *e);

typedef struct {
  INT reserved;
} MCastReadyToSendEventParams;

#define EID_MCAST_READYTOSEND 3

virtual INT IPWORKS_CALL FireReadyToSend();

class MCastReadyToSendEventParams {
public:
  int EventRetVal();
  void SetEventRetVal(int iRetVal);
};

// To handle, connect one or more slots to this signal.
void ReadyToSend(MCastReadyToSendEventParams *e);

// Or, subclass MCast and override this emitter function.
virtual int FireReadyToSend(MCastReadyToSendEventParams *e) {...}

Remarks

The ReadyToSend event indicates that the underlying Transmission Control Protocol (TCP)/IP subsystem is ready to accept data after a failed Send.

Config Settings (MCast Class)

UDP Config Settings

Socket Config Settings

Base Config Settings

Trappable Errors (MCast Class)

Error Handling (C++)

Call the GetLastErrorCode() method to obtain the last called method's result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. Known error codes are listed below. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.

MCast Errors

SSL Errors

TCP/IP Errors