ICMP Class

Properties   Methods   Events   Config Settings   Errors  

The ICMP class is used to facilitate ICMP communications. It can act both as a client and a server and can communicate with any number of hosts simultaneously. It also can generate and receive broadcast packets.

Syntax

ICMP

Remarks

The interface of the class is similar to the interface of TCPClient, only it is much simpler. The class is activated/deactivated by using the Active property. This property enables or disables the sending or receiving of data. Data can be sent in the same way as TCPClient, using the Send method and Text parameter or the DataToSend property. The destination is specified using the RemoteHost property. The class automatically creates an ICMP header containing MessageType, MessageSubType, and a checksum for the message.

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 can send datagrams to any host. Packets can be broadcast on the local net by setting the destination to 255.255.255.255.

Inbound data is received through the DataIn event.

The operation of the class is almost completely asynchronous. All the 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 with 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 (ICMP Class)

This property enables or disables data reception (the DataIn event).

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetAcceptData();
int SetAcceptData(int bAcceptData);

Unicode (Windows)
BOOL GetAcceptData();
INT SetAcceptData(BOOL bAcceptData);

int ipworks_icmp_getacceptdata(void* lpObj);
int ipworks_icmp_setacceptdata(void* lpObj, int bAcceptData);

bool GetAcceptData();
int SetAcceptData(bool bAcceptData);

Default Value

TRUE

Remarks

This property enables or disables data reception (the DataIn event). Setting this property to False, temporarily disables data reception (and the DataIn event). Setting this property to True, reenables data reception.

Note: It is recommended to use the PauseData or ProcessData method instead of setting this property.

This property is not available at design time.

Data Type

Boolean

Active Property (ICMP Class)

This property indicates whether the class is active.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetActive();
int SetActive(int bActive);

Unicode (Windows)
BOOL GetActive();
INT SetActive(BOOL bActive);

int ipworks_icmp_getactive(void* lpObj);
int ipworks_icmp_setactive(void* lpObj, int bActive);

bool GetActive();
int SetActive(bool bActive);

Default Value

FALSE

Remarks

This property indicates whether the class is currently active and can send or receive data.

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

Note: Use the Activate or Deactivate method to control whether the class is active.

This property is not available at design time.

Data Type

Boolean

DataToSend Property (ICMP Class)

This write-only property includes a string of data to be sent to the remote host.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int SetDataToSend(const char* lpDataToSend, int lenDataToSend);

Unicode (Windows)
INT SetDataToSend(LPCSTR lpDataToSend, INT lenDataToSend);

int ipworks_icmp_setdatatosend(void* lpObj, const char* lpDataToSend, int lenDataToSend);

int SetDataToSend(QByteArray qbaDataToSend);

Default Value

""

Remarks

This property is write-only and contains a string of data to be sent to the remote host. Assigning a string to this property makes the class send the string to the remote host. The Send method provides similar functionality.

The Transmission Control Protocol (TCP)/IP subsystem attempts to send the string assigned to this property as a complete message. If socket buffers are full, or if the message cannot be delivered for any other reason, an error is fired, and no portion of the message is sent. This is different from TCP in which case portions of the messages can be sent. ICMP sends either a complete message or nothing at all.

If you are sending data to the remote host faster than it can process it, or faster than the network's bandwidth allows, the outgoing queue might fill up. When this happens, DataToSend fails with error 10035: "[10035] Operation would block" (WSAEWOULDBLOCK). You can check this error, and then try to send the data again. .

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

Data Type

Binary String

DontRoute Property (ICMP 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_icmp_getdontroute(void* lpObj);
int ipworks_icmp_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 (ICMP 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_icmp_getlocalhost(void* lpObj);
int ipworks_icmp_setlocalhost(void* lpObj, const char* lpszLocalHost);

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

Default Value

""

Remarks

The LocalHost 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 multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the class initiate connections (or accept in the case of server classs) only through that interface.

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 multi-homed 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

MessageSubType Property (ICMP Class)

This property is the subtype of the ICMP message (part of the ICMP header).

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetMessageSubType();
int SetMessageSubType(int iMessageSubType);

Unicode (Windows)
INT GetMessageSubType();
INT SetMessageSubType(INT iMessageSubType);

int ipworks_icmp_getmessagesubtype(void* lpObj);
int ipworks_icmp_setmessagesubtype(void* lpObj, int iMessageSubType);

int GetMessageSubType();
int SetMessageSubType(int iMessageSubType);

Default Value

0

Remarks

This property contains the subtype of the ICMP message (part of the ICMP header). The ICMP message subtype (also referred to as "code") is a byte value representing the message subclass. Its meaning is associated with the MessageType.

Types and subtypes of ICMP messages are defined in the various internet RFCs and other documentation associated with Transmission Control Protocol (TCP)/IP.

Data Type

Integer

MessageType Property (ICMP Class)

This property includes the type of the ICMP message (part of the ICMP header).

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetMessageType();
int SetMessageType(int iMessageType);

Unicode (Windows)
INT GetMessageType();
INT SetMessageType(INT iMessageType);

int ipworks_icmp_getmessagetype(void* lpObj);
int ipworks_icmp_setmessagetype(void* lpObj, int iMessageType);

int GetMessageType();
int SetMessageType(int iMessageType);

Default Value

0

Remarks

This property contains the type of the ICMP message (part of the ICMP header). The ICMP message type is a byte value representing the message class. The message type defines the structure and meaning of the message data assigned to DataToSend.

Types for ICMP messages are defined in the various internet RFCs and other documentation associated with Transmission Control Protocol (TCP/IP). The following are a few examples of ICMP message types:

Data Type

Integer

RemoteHost Property (ICMP Class)

This property includes the address of the RemoteHost. 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_icmp_getremotehost(void* lpObj);
int ipworks_icmp_setremotehost(void* lpObj, const char* lpszRemoteHost);

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

Default Value

""

Remarks

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

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

If this property is set to a domain name, a DNS request is initiated. Upon successful termination of the request, the property is set to the corresponding address. If the search is not successful, the class fails with an error.

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

Data Type

String

Timeout Property (ICMP Class)

A timeout for the class.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int GetTimeout();
int SetTimeout(int iTimeout);

Unicode (Windows)
INT GetTimeout();
INT SetTimeout(INT iTimeout);

int ipworks_icmp_gettimeout(void* lpObj);
int ipworks_icmp_settimeout(void* lpObj, int iTimeout);

int GetTimeout();
int SetTimeout(int iTimeout);

Default Value

0

Remarks

If the Timeout property is set to 0, all operations return immediately, potentially failing with an 'WOULDBLOCK' error if data can't be sent or received immediately.

If Timeout is set to a positive value, the class will automatically retry each operation that would otherwise result in a 'WOULDBLOCK' error for a maximum of Timeout seconds.

The class will use DoEvents to enter an efficient wait loop during any potential waiting period, making sure that all system events are processed immediately as they arrive. This ensures that the host application does not "freeze" and remains responsive.

If Timeout expires, and the operation is not yet complete, the class fails with an error.

Please note that by default, all timeouts are inactivity timeouts, i.e. the timeout period is extended by Timeout seconds when any amount of data is successfully sent or received.

The default value for the Timeout property is 0 (asynchronous operation).

Data Type

Integer

TimeToLive Property (ICMP Class)

This property includes the time-to-live (TTL) value for the ICMP packets sent by the class.

Syntax

• C++
• C
• Qt

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

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

int ipworks_icmp_gettimetolive(void* lpObj);
int ipworks_icmp_settimetolive(void* lpObj, int iTimeToLive);

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

Default Value

0

Remarks

This method contains the time-to-live (TTL) value for the ICMP packets sent by the class. The TTL field of the ICMP packet is a counter limiting the lifetime of a packet.

Each router (or other module) that handles a packet decrements the TTL field by one or more if it holds the packet for more than one second. Thus, the TTL value is effectively a hop count limit on how far a datagram can propagate through the internet. When the TTL value is reduced to zero (or less), the packet is discarded.

If the value of the property is set to zero, then the default TTL value of the underlying Transmission Control Protocol (TCP)/IP subsystem will be used.

This property is not available at design time.

Data Type

Integer

Activate Method (ICMP Class)

This method enables sending and receiving of data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Activate();

Unicode (Windows)
INT Activate();

int ipworks_icmp_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 ICMP 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 also is 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 (ICMP 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_icmp_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 (ICMP Class)

This method disables sending and receiving of data.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Deactivate();

Unicode (Windows)
INT Deactivate();

int ipworks_icmp_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 (ICMP Class)

Processes events from the internal message queue.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int DoEvents();

Unicode (Windows)
INT DoEvents();

int ipworks_icmp_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 (ICMP Class)

This method pauses data reception.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int PauseData();

Unicode (Windows)
INT PauseData();

int ipworks_icmp_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 (ICMP 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_icmp_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 (ICMP Class)

Reset the class.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int Reset();

Unicode (Windows)
INT Reset();

int ipworks_icmp_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 (ICMP Class)

Resolves the hostname in RemoteHost to an IP address.

Syntax

• C++
• C
• Qt

ANSI (Cross Platform)
int ResolveRemoteHost();

Unicode (Windows)
INT ResolveRemoteHost();

int ipworks_icmp_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 necessary. 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 (ICMP 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_icmp_send(void* lpObj, const char* lpText, int lenText);

int Send(QByteArray qbaText);

Remarks

This method sends data to the remote host. Calling this method is equivalent to setting the DataToSend property to Text.

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 (ICMP 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_icmp_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 (ICMP 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_icmp_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 (ICMP Class)

This event is fired when a new ICMP messages come in.

Syntax

• C++
• C
• Qt

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

typedef struct {
  int MessageType;
  int MessageSubType;
  const char *MessageData;
  int lenMessageData;
  int Checksum;
  const char *SourceAddress;
  int reserved;
} ICMPDataInEventParams;


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

typedef struct {
  INT MessageType;
  INT MessageSubType;
  LPCSTR MessageData;
  INT lenMessageData;
  INT Checksum;
  LPCWSTR SourceAddress;
  INT reserved;
} ICMPDataInEventParams;

#define EID_ICMP_DATAIN 1

virtual INT IPWORKS_CALL FireDataIn(INT &iMessageType, INT &iMessageSubType, LPSTR &lpMessageData, INT &lenMessageData, INT &iChecksum, LPSTR &lpszSourceAddress);

class ICMPDataInEventParams {
public:
  int MessageType();

  int MessageSubType();

  const QByteArray &MessageData();

  int Checksum();

  const QString &SourceAddress();

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

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

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

Remarks

The MessageType parameter shows the type of the ICMP messages and the MessageSubType parameter shows its subtype.

The MessageData parameter contains the message data.

The Checksum parameter is True or False depending on the ICMP checksum validation on the message.

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 (ICMP Class)

Fired when information is available about errors during data delivery.

Syntax

• C++
• C
• Qt

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

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


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

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

#define EID_ICMP_ERROR 2

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

class ICMPErrorEventParams {
public:
  int ErrorCode();

  const QString &Description();

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

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

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

Fired when the class is ready to send data.

Syntax

• C++
• C
• Qt

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

typedef struct {
  int reserved;
} ICMPReadyToSendEventParams;


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

typedef struct {
  INT reserved;
} ICMPReadyToSendEventParams;

#define EID_ICMP_READYTOSEND 3

virtual INT IPWORKS_CALL FireReadyToSend();

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

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

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

Remarks

The ReadyToSend event indicates that the underlying TCP/IP subsystem is ready to accept data after a failed DataToSend.

Config Settings (ICMP Class)

ICMP Config Settings

Socket Config Settings

Base Config Settings

Trappable Errors (ICMP 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.

ICMP Errors

SSL Errors

TCP/IP Errors