UDP Class

Properties   Methods   Events   Config Settings   Errors  

The User Datagram Protocol (UDP) class is used to facilitate UDP (datagram) communications. It can act both as a client and a server and communicate with any number of hosts simultaneously, as well as generate and receive broadcast packets.

Syntax

UDP

Remarks

The interface of the class is similar to the interface of TCPClient, only much simpler. The class is activated or deactivated through the Active property. This property enables or disables sends or receives. The data can be sent in the same way as TCPClient, using the Send method and specifying the text to send. The destination is specified using the RemoteHost and RemotePort properties. Inbound data are received through the DataIn event.

If the UseConnection configuration setting is set to True, then a local association is created with the remote host. Otherwise, the class can receive datagrams (packets) from any host, and send datagrams to any host. Packets can be broadcast on the local net by setting the destination (RemoteHost) to 255.255.255.255.

The operation of the class is almost completely asynchronous. All calls, except the ones that deal with domain name resolution, operate through Windows messages (no blocking calls). The gain in performance is considerable when compared to using blocking calls.

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 (UDP 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_udp_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 (UDP Class)

This property indicates whether the class is active.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetActive();

Unicode (Windows)
BOOL GetActive();

int ipworks_udp_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

DontRoute Property (UDP Class)

If this property is set to True, it forces the socket to send data directly to the interface (no routing).

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetDontRoute();
int SetDontRoute(int bDontRoute);

Unicode (Windows)
BOOL GetDontRoute();
INT SetDontRoute(BOOL bDontRoute);

int ipworks_udp_getdontroute(void* lpObj);
int ipworks_udp_setdontroute(void* lpObj, int bDontRoute);

bool GetDontRoute();
int SetDontRoute(bool bDontRoute);

Default Value

FALSE

Remarks

If this property is set to True, it forces the socket to send data directly to the interface (no routing). Normally, IP sockets send packets of data through routers and gateways until they reach the final destination. If this property is set to True, then data will be delivered on the local subnet only.

This property is not available at design time.

Data Type

Boolean

LocalHost Property (UDP 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_udp_getlocalhost(void* lpObj);
int ipworks_udp_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 (UDP Class)

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

Syntax

• C++
• C
• Qt

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

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

int ipworks_udp_getlocalport(void* lpObj);
int ipworks_udp_setlocalport(void* lpObj, int iLocalPort);

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

Default Value

0

Remarks

The LocalPort property must be set before UDP is activated (Active is set to True). This instructs the class to bind to a specific port (or communication endpoint) in the local machine.

Setting it to 0 (default) enables the Transmission Control Protocol (TCP)/IP stack to choose a port at random. The chosen port will be shown by the LocalPort property after the connection is established.

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

The LocalPort property is useful when trying to connect to services that require a trusted port on the client side.

Data Type

Integer

RemoteHost Property (UDP Class)

This property includes the address of the remote host. Domain names are resolved to IP addresses.

Syntax

• C++
• C
• Qt

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

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

char* ipworks_udp_getremotehost(void* lpObj);
int ipworks_udp_setremotehost(void* lpObj, const char* lpszRemoteHost);

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

Default Value

""

Remarks

The RemoteHost property specifies the IP address (IP number in dotted internet format) or domain name of the remote host.

If RemoteHost is set to 255.255.255.255, the class broadcasts data on the local subnet.

If the RemoteHost property is set to a domain name, a DNS request is initiated, and upon successful termination of the request, the RemoteHost property is set to the corresponding address. If the search is not successful, an error is returned.

If UseConnection is set to True, the RemoteHost must be set before the class is activated (Active is set to True).

Data Type

String

RemotePort Property (UDP Class)

This property specifies the User Datagram Protocol (UDP) port in 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_udp_getremoteport(void* lpObj);
int ipworks_udp_setremoteport(void* lpObj, int iRemotePort);

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

Default Value

0

Remarks

The RemotePort is the UDP port on the RemoteHost to send UDP datagrams to.

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

If UseConnection is set to True, the RemotePort must be set before the class is activated (Active is set to True).

Data Type

Integer

TimeToLive Property (UDP Class)

This property specifies the maximum number of subnets that a 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_udp_gettimetolive(void* lpObj);
int ipworks_udp_settimetolive(void* lpObj, int iTimeToLive);

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

Default Value

0

Remarks

The default value for this property is 0, which tells the class to use the default time-to-live (TTL) value of the underlying Transmission Control Protocol (TCP)/IP subsystem. Depending on the application, you can specify a value between 1 and 255.

Data Type

Integer

Activate Method (UDP Class)

This method enables sending and receiving of data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Activate();

Unicode (Windows)
INT Activate();

int ipworks_udp_activate(void* lpObj);

int Activate();

Remarks

This method enables sending and receiving of data. When called, the class will create a communication endpoint (socket) that can be used for sending and receiving User Datagram Protocol (UDP) messages. This method must be called before using the class to send and receive data.

If the UseConnection configuration setting is set to true, then a local association (connection) to the remote host is also created.

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 (UDP 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_udp_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 (UDP Class)

This method disables sending and receive of data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Deactivate();

Unicode (Windows)
INT Deactivate();

int ipworks_udp_deactivate(void* lpObj);

int Deactivate();

Remarks

This method disables sending and receiving of data. When called, the class 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 (UDP 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_udp_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 (UDP Class)

This method pauses data reception.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int PauseData();

Unicode (Windows)
INT PauseData();

int ipworks_udp_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 (UDP 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_udp_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 (UDP Class)

This method will reset the class.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Reset();

Unicode (Windows)
INT Reset();

int ipworks_udp_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 (UDP 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_udp_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 (UDP Class)

This method sends binary 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_udp_send(void* lpObj, const char* lpText, int lenText);

int Send(QByteArray qbaText);

Remarks

This method sends the specified binary data to the remote host. To send text, use the SendText method instead.

Example. Send Data:

UDPControl.LocalPort = 8765 UDPControl.RemotePort = 8765 UDPControl.RemoteHost = "HostNameOrIPAddress" UDPControl.Active = True UDPControl.SendText("Hello!")

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 (UDP Class)

This method sends binary 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_udp_sendbytes(void* lpObj, const char* lpData, int lenData);

int SendBytes(QByteArray qbaData);

Remarks

This method sends the specified binary data to the remote host. To send text, use the SendText method instead.

Example. Send Data:

UDPControl.LocalPort = 8765 UDPControl.RemotePort = 8765 UDPControl.RemoteHost = "HostNameOrIPAddress" UDPControl.Active = True UDPControl.SendText("Hello!")

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 (UDP Class)

This method sends text to the remote host.

Syntax

• C++
• C
• Qt

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

Unicode (Windows)
INT SendText(LPCWSTR lpszText);

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

int SendText(const QString& qsText);

Remarks

This method sends the specified text to the remote host. To send binary data, use the SendBytes method instead.

Example. Send Data:

UDPControl.LocalPort = 8765 UDPControl.RemotePort = 8765 UDPControl.RemoteHost = "HostNameOrIPAddress" UDPControl.Active = True UDPControl.SendText("Hello!")

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 (UDP Class)

This event is fired when data are received.

Syntax

• C++
• C
• Qt

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

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


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

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

#define EID_UDP_DATAIN 1

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

class UDPDataInEventParams {
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(UDPDataInEventParams *e);

// Or, subclass UDP and override this emitter function.
virtual int FireDataIn(UDPDataInEventParams *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 (UDP Class)

Fired when information is available about errors during data delivery.

Syntax

• C++
• C
• Qt

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

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


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

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

#define EID_UDP_ERROR 2

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

class UDPErrorEventParams {
public:
  int ErrorCode();

  const QString &Description();

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

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

// Or, subclass UDP and override this emitter function.
virtual int FireError(UDPErrorEventParams *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 (UDP Class)

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

Syntax

• C++
• C
• Qt

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

typedef struct {
  int reserved;
} UDPReadyToSendEventParams;


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

typedef struct {
  INT reserved;
} UDPReadyToSendEventParams;

#define EID_UDP_READYTOSEND 3

virtual INT IPWORKS_CALL FireReadyToSend();

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

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

// Or, subclass UDP and override this emitter function.
virtual int FireReadyToSend(UDPReadyToSendEventParams *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 (UDP Class)

UDP Config Settings

Socket Config Settings

Base Config Settings

Trappable Errors (UDP 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.

UDP Errors

SSL Errors

TCP/IP Errors