Class RHostResolver

class RHostResolver : public RSubSessionBase;

Support

Supported from 5.0

Description

Provides an interface to host name resolution services, such as DNS, that may be provided by particular protocol modules.

The interface provides functions to access the following facilities:

• Obtaining names from addresses.

• Obtaining addresses from names.

• Getting and setting local host name.

Not all actual services provide all these facilities. You should also consult the documentation on the protocol you are intending to use. Functions return KErrNotSupported if the protocol does not support a given operation. Note that a description of the protocol family name resolution capabilities is available at run-time from TProtocolDesc::iNamingServices.

Derivation

RHostResolver Provides an interface to host name resolution services, such as DNS, that may be provided by particular protocol modules RSubSessionBase Client-side handle to a sub-session

Defined in RHostResolver:
Cancel(), Close(), GetByAddress(), GetByAddress(), GetByName(), GetHostName(), GetHostName(), Next(), Next(), Open(), SetHostName()

Inherited from RSubSessionBase:
CloseSubSession(), CreateSubSession(), Send(), SendReceive(), SubSessionHandle(), operator=()

Notes:

• Before using any service, a connection to a socket server session must be made.
• Each function is available in both synchronous and asynchronous versions.
• A single RHostResolver can only perform one request of any type at once. A client is panicked if it makes two requests.

TInt Open(RSocketServ& aSocketServer,TUint anAddrFamily,TUint aProtocol);

Description

Initialises a name resolution service provided by a particular protocol. It must be called before other object functions are used.

Parameters

RSocketServ& aSocketServer The socket server session TUint anAddrFamily A constant identifying the protocol family TUint aProtocol A constant that identifies the protocol that provides the name resolution service

Return value

TInt KErrNone if successful otherwise another of the system-wide error codes.

void Close();

Description

Closes a name resolution service. If a service has been opened using Open(), then it should be closed using Close(). This will ensure all associated resources are released.

void GetByAddress(const TSockAddr& anAddr,TNameEntry& aResult,TRequestStatus& aStatus);

Description

Gets the name of a host from its address asynchronously.

Parameters

const TSockAddr& anAddr The address to use TNameEntry& aResult On return, the result of the query. If more than one result is allowed by the protocol, the client can call Next() to find any further results. TRequestStatus& aStatus Indicates asynchronous operation and on completion contains an error code: see the system-wide error codes.

TInt GetByAddress(const TSockAddr& anAddr,TNameEntry& aResult);

Description

Gets the name of a host from its address.

Parameters

const TSockAddr& anAddr The address to use TNameEntry& aResult Returns the result of the query. If more than one result is allowed by the protocol, the client can call Next() to find any further results.

Return value

TInt KErrNone if successful otherwise another of the system-wide error codes.

void GetByName(const TDesC& aName,TNameEntry& aResult,TRequestStatus& aStatus);

Description

Resolves a machine name to a TSockAddress asynchronously.

Parameters

const TDesC& aName The name to resolve. The format of the name and any wild-cards supported, along with any separators in hierarchical name systems, are protocol specific TNameEntry& aResult On return, the result of the name resolution. If more than one result is allowed by the protocol, the client can call Next() to find any further results. TRequestStatus& aStatus Indicates asynchronous operation and, on completion, contains an error code: see the system-wide error codes.

TInt Next(TNameEntry& aResult);

Description

Returns the next answer. For some protocols, GetByName() and GetByAddress() may find more than one answer, for example if aliases are allowed.

Parameters

TNameEntry& aResult Returns the next result of the name resolution.

Return value

TInt KErrNone if successful otherwise another of the system-wide error codes.

void Next(TNameEntry& aResult,TRequestStatus& aStatus);

Description

Returns the next answer asynchronously. For some protocols, GetByName() and GetByAddress() may find more than one answer, for example if aliases are allowed.

Parameters

TNameEntry& aResult Returns the next result of the name resolution. TRequestStatus& aStatus Indicates asynchronous operation and on completion contains an error code: see the system-wide error codes.

TInt GetHostName(TDes& aName);

Description

Gets the name of the local host.

Note that with some protocols the name of the local host is not necessarily known at all times. In some cases, a preceding call to SetHostName() must have been made.

Parameters

TDes& aName Returns the result of the query. The buffer passed in should have a minimum length of 256 characters, otherwise a panic may occur: you can use a parameter of the THostName type.

Return value

TInt KErrNone if successful otherwise another of the system-wide error codes.

void GetHostName(TDes& aName,TRequestStatus &aStatus);

Description

Gets the name of the local host asynchronously.

Note that with some protocols the name of the local host is not necessarily known at all times. In some cases, a preceding call to SetHostName() must have been made.

Parameters

TDes& aName Returns the result of the query. The buffer passed in should have a minimum length of 256 characters, otherwise a panic may occur: you can use a parameter of the THostName type. TRequestStatus& aStatus Indicates asynchronous operation and on completion contains an error code: see the system-wide error codes.

TInt SetHostName(const TDesC& aName);

Description

Sets the name of the local host.

Parameters

const TDesC& aName The local host name

Return value

TInt KErrNone if successful otherwise another of the system-wide error codes.

void Cancel();

Description

Cancels any outstanding asynchronous calls, which will return with error code KErrCancel.