glibmm: Gio::Socket Class Reference

Low-level socket object. More...

#include <giomm/socket.h>

Inheritance diagram for Gio::Socket:

Public Member Functions
virtual	~Socket ()
GSocket*	gobj ()
	Provides access to the underlying C GObject.
const GSocket*	gobj () const
	Provides access to the underlying C GObject.
GSocket*	gobj_copy ()
	Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs.
void	bind (const Glib::RefPtr< SocketAddress >& address, bool allow_reuse)
	When a socket is created it is attached to an address family, but it doesn't have an address in this family.
void	listen ()
	Marks the socket as a server socket, i.e. a socket that is used to accept incoming requests using g_socket_accept().
Glib::RefPtr< Socket >	accept (const Glib::RefPtr< Cancellable >& cancellable)
	Accept incoming connections on a connection-based socket.
Glib::RefPtr< Socket >	accept ()
void	connect (const Glib::RefPtr< SocketAddress >& address, const Glib::RefPtr< Cancellable >& cancellable)
	Connect the socket to the specified remote address.
void	connect (const Glib::RefPtr< SocketAddress >& address)
void	check_connect_result ()
	Checks and resets the pending connect error for the socket.
gssize	receive (char* buffer, gsize size, const Glib::RefPtr< Cancellable >& cancellable)
	Receive data (up to size bytes) from a socket.
gssize	receive (char* buffer, gsize size)
gssize	receive_from (Glib::RefPtr< SocketAddress >& address, char* buffer, gsize size, const Glib::RefPtr< Cancellable >& cancellable)
gssize	receive_from (Glib::RefPtr< SocketAddress >& address, char* buffer, gsize size)
gssize	send (const gchar* buffer, gsize size, const Glib::RefPtr< Cancellable >& cancellable)
	Tries to send size bytes from buffer on the socket.
gssize	send (const gchar* buffer, gsize size)
gssize	send_to (const Glib::RefPtr< SocketAddress >& address, const char* buffer, gsize size, const Glib::RefPtr< Cancellable >& cancellable)
	Tries to send size bytes from buffer to address.
gssize	send_to (const Glib::RefPtr< SocketAddress >& address, const char* buffer, gsize size)
void	close ()
	Closes the socket, shutting down any active connection.
bool	is_closed ()
	Checks whether a socket is closed.
void	shutdown (bool shutdown_read, bool shutdown_write)
	Shut down part of a full-duplex connection.
bool	is_connected ()
	Check whether the socket is connected.
Glib::IOCondition	condition_check (Glib::IOCondition condition)
	Checks on the readiness of socket to perform operations.
void	condition_wait (Glib::IOCondition condition, const Glib::RefPtr< Cancellable >& cancellable)
	Waits for condition to become true on socket.
void	condition_wait (Glib::IOCondition condition)
void	set_listen_backlog (int backlog)
	Sets the maximum number of outstanding connections allowed when listening on this socket.
int	get_listen_backlog () const
	Gets the listen backlog setting of the socket.
void	set_blocking (bool blocking)
	Sets the blocking mode of the socket.
bool	get_blocking () const
	Gets the blocking mode of the socket.
void	set_keepalive (bool keepalive)
	Sets or unsets the So::KEEPALIVE flag on the underlying socket.
bool	get_keepalive () const
	Gets the keepalive mode of the socket.
SocketFamily	get_family () const
	Gets the socket family of the socket.
int	get_fd () const
	Returns the underlying OS socket object.
Glib::RefPtr< SocketAddress >	get_local_address () const
	Try to get the local address of a bound socket.
Glib::RefPtr< SocketAddress >	get_remote_address () const
	Try to get the remove address of a connected socket.
SocketProtocol	get_protocol () const
	Gets the socket protocol id the socket was created with.
SocketType	get_socket_type () const
	Gets the socket type of the socket.
bool	speaks_ipv4 () const
	Checks if a socket is capable of speaking IPv4.
Glib::RefPtr< Credentials >	get_credentials ()
	Returns the credentials of the foreign process connected to this socket, if any (e.g. it is only supported for SOCKET_FAMILY_UNIX sockets).
Glib::RefPtr< const Credentials >	get_credentials () const
	Returns the credentials of the foreign process connected to this socket, if any (e.g. it is only supported for SOCKET_FAMILY_UNIX sockets).
guint	get_timeout () const
	Gets the timeout setting of the socket.
void	set_timeout (guint timeout)
	Sets the time in seconds after which I/O operations on socket will time out if they have not yet completed.
gssize	receive_with_blocking (gchar* buffer, gsize size, bool blocking, const Glib::RefPtr< Cancellable >& cancellable=Glib::RefPtr< Cancellable >())
	This behaves exactly the same as g_socket_receive(), except that the choice of blocking or non-blocking behavior is determined by the blocking argument rather than by socket's properties.
gssize	send_with_blocking (gchar* buffer, gsize size, bool blocking, const Glib::RefPtr< Cancellable >& cancellable=Glib::RefPtr< Cancellable >())
	This behaves exactly the same as g_socket_send(), except that the choice of blocking or non-blocking behavior is determined by the blocking argument rather than by socket's properties.
Glib::PropertyProxy< bool >	property_blocking ()
	Whether or not I/O on this socket is blocking.
Glib::PropertyProxy_ReadOnly < bool >	property_blocking () const
	Whether or not I/O on this socket is blocking.
Glib::PropertyProxy_ReadOnly < SocketFamily >	property_family () const
	The sockets address family.
Glib::PropertyProxy_ReadOnly< int >	property_fd () const
	The sockets file descriptor.
Glib::PropertyProxy< bool >	property_keepalive ()
	Keep connection alive by sending periodic pings.
Glib::PropertyProxy_ReadOnly < bool >	property_keepalive () const
	Keep connection alive by sending periodic pings.
Glib::PropertyProxy< int >	property_listen_backlog ()
	Outstanding connections in the listen queue.
Glib::PropertyProxy_ReadOnly< int >	property_listen_backlog () const
	Outstanding connections in the listen queue.
Glib::PropertyProxy_ReadOnly < Glib::RefPtr< SocketAddress > >	property_local_address () const
	The local address the socket is bound to.
Glib::PropertyProxy_ReadOnly < Glib::RefPtr< SocketAddress > >	property_remote_address () const
	The remote address the socket is connected to.
Glib::PropertyProxy_ReadOnly < SocketProtocol >	property_protocol () const
	The id of the protocol to use, or -1 for unknown.
Glib::PropertyProxy_ReadOnly < SocketType >	property_type () const
	The sockets type.
Static Public Member Functions
static Glib::RefPtr< Socket >	create (SocketFamily family, SocketType type, SocketProtocol protocol, const Glib::RefPtr< Cancellable >& cancellable=Glib::RefPtr< Cancellable >())
	Creates a new Socket with the defined family, type and protocol.
static Glib::RefPtr< Socket >	create_from_fd (int fd, const Glib::RefPtr< Cancellable >& cancellable=Glib::RefPtr< Cancellable >())
	Creates a new Socket from a native file descriptor or winsock SOCKET handle.
Protected Member Functions
	Socket (SocketFamily family, SocketType type, SocketProtocol protocol, const Glib::RefPtr< Cancellable >& cancellable)
	Socket (int fd, const Glib::RefPtr< Cancellable >& cancellable)
Related Functions
(Note that these are not member functions.)
Glib::RefPtr< Gio::Socket >	wrap (GSocket* object, bool take_copy=false)
	A Glib::wrap() method for this object.

Detailed Description

Low-level socket object.

A Socket is a low-level networking primitive. It is a more or less direct mapping of the BSD socket API in a portable GObject based API. It supports both the UNIX socket implementations and winsock2 on Windows.

Socket is the platform independent base upon which the higher level network primitives are based. Applications are not typically meant to use it directly, but rather through classes like SocketClient, SocketService and SocketConnection. However there may be cases where direct use of Socket is useful.

Socket implements the Initable interface, and since initialization can fail, the constructor may throw an exception.

Sockets operate in two general modes, blocking or non-blocking. When in blocking mode all operations block until the requested operation is finished or there is an error. In non-blocking mode all calls that would block return immediately with a Gio::Error::WOULD_BLOCK error. To know when a call would successfully run you can call condition_check(), or condition_wait(). You can also use create_source() and attach it to a Glib::MainContext to get callbacks when I/O is possible. Note that all sockets are always set to non blocking mode in the system, and blocking mode is emulated in Socket.

When working in non-blocking mode applications should always be able to handle getting a Gio::Error::WOULD_BLOCK error even when some other function said that I/O was possible. This can easily happen in case of a race condition in the application, but it can also happen for other reasons. For instance, on Windows a socket is always seen as writable until a write returns Gio::Error::WOULD_BLOCK.

Sockets can be either connection oriented or datagram based. For connection oriented types you must first establish a connection by either connecting to an address or accepting a connection from another address. For connectionless socket types the target/source address is specified or received in each I/O operation.

All socket file descriptors are set to be close-on-exec.

Note that creating a Socket causes the signal SIGPIPE to be ignored for the remainder of the program. If you are writing a command-line utility that uses Socket, you may need to take into account the fact that your program will not automatically be killed if it tries to write to stdout after it has been closed.

Since glibmm 2.24:

Constructor & Destructor Documentation

virtual Gio::Socket::~Socket ( ) [virtual]

Gio::Socket::Socket	(	SocketFamily	family,
		SocketType	type,
		SocketProtocol	protocol,
		const Glib::RefPtr< Cancellable >&	cancellable
	)		`[protected]`

Gio::Socket::Socket	(	int	fd,
		const Glib::RefPtr< Cancellable >&	cancellable
	)		`[protected]`

Member Function Documentation

Glib::RefPtr<Socket> Gio::Socket::accept ( const Glib::RefPtr< Cancellable >& cancellable )

Accept incoming connections on a connection-based socket.

This removes the first outstanding connection request from the listening socket and creates a Socket object for it.

The socket must be bound to a local address with g_socket_bind() and must be listening for incoming connections (g_socket_listen()).

If there are no outstanding connections then the operation will block or return IO_ERROR_WOULD_BLOCK if non-blocking I/O is enabled. To be notified of an incoming connection, wait for the IO_IN condition.

Since glibmm 2.22:

Parameters:

cancellable A Cancellable or 0.

Returns:: A new Socket, or 0 on error. Free the returned object with Glib::object_unref().

Glib::RefPtr<Socket> Gio::Socket::accept ( )

void Gio::Socket::bind	(	const Glib::RefPtr< SocketAddress >&	address,
		bool	allow_reuse
	)

When a socket is created it is attached to an address family, but it doesn't have an address in this family.

g_socket_bind() assigns the address (sometimes called name) of the socket.

It is generally required to bind to a local address before you can receive connections. (See g_socket_listen() and g_socket_accept() ). In certain situations, you may also want to bind a socket that will be used to initiate connections, though this is not normally required.

allow_reuse should be true for server sockets (sockets that you will eventually call g_socket_accept() on), and false for client sockets. (Specifically, if it is true, then g_socket_bind() will set the So::REUSEADDR flag on the socket, allowing it to bind address even if that address was previously used by another socket that has not yet been fully cleaned-up by the kernel. Failing to set this flag on a server socket may cause the bind call to return IO_ERROR_ADDRESS_IN_USE if the server program is stopped and then immediately restarted.)

Since glibmm 2.22:

Parameters:

address	A SocketAddress specifying the local address.
allow_reuse	Whether to allow reusing this address.

Returns:: true on success, false on error.

void Gio::Socket::check_connect_result ( )

Checks and resets the pending connect error for the socket.

This is used to check for errors when g_socket_connect() is used in non-blocking mode.

Since glibmm 2.22:

Returns:: true if no error, false otherwise, setting error to the error.

void Gio::Socket::close ( )

Closes the socket, shutting down any active connection.

Closing a socket does not wait for all outstanding I/O operations to finish, so the caller should not rely on them to be guaranteed to complete even if the close returns with no error.

Once the socket is closed, all other operations will return IO_ERROR_CLOSED. Closing a socket multiple times will not return an error.

Sockets will be automatically closed when the last reference is dropped, but you might want to call this function to make sure resources are released as early as possible.

Beware that due to the way that TCP works, it is possible for recently-sent data to be lost if either you close a socket while the IO_IN condition is set, or else if the remote connection tries to send something to you after you close the socket but before it has finished reading all of the data you sent. There is no easy generic way to avoid this problem; the easiest fix is to design the network protocol such that the client will never send data "out of turn". Another solution is for the server to half-close the connection by calling g_socket_shutdown() with only the shutdown_write flag set, and then wait for the client to notice this and close its side of the connection, after which the server can safely call g_socket_close(). (This is what TcpConnection does if you call g_tcp_connection_set_graceful_disconnect(). But of course, this only works if the client will close its connection after the server does.)

Since glibmm 2.22:

Returns:: true on success, false on error.

Glib::IOCondition Gio::Socket::condition_check ( Glib::IOCondition condition )

Checks on the readiness of socket to perform operations.

The operations specified in condition are checked for and masked against the currently-satisfied conditions on socket. The result is returned.

Note that on Windows, it is possible for an operation to return IO_ERROR_WOULD_BLOCK even immediately after g_socket_condition_check() has claimed that the socket is ready for writing. Rather than calling g_socket_condition_check() and then writing to the socket if it succeeds, it is generally better to simply try writing to the socket right away, and try again later if the initial attempt returns IO_ERROR_WOULD_BLOCK.

It is meaningless to specify IO_ERR or IO_HUP in condition; these conditions will always be set in the output if they are true.

This call never blocks.

Since glibmm 2.22:

Parameters:

condition A IOCondition mask to check.

Returns:: The GIOCondition mask of the current state.

void Gio::Socket::condition_wait	(	Glib::IOCondition	condition,
		const Glib::RefPtr< Cancellable >&	cancellable
	)

Waits for condition to become true on socket.

When the condition is met, true is returned.

If cancellable is cancelled before the condition is met, or if the socket has a timeout set and it is reached before the condition is met, then false is returned and error, if non-0, is set to the appropriate value (IO_ERROR_CANCELLED or IO_ERROR_TIMED_OUT).

Since glibmm 2.22:

Parameters:

condition	A IOCondition mask to wait for.
cancellable	A Cancellable, or `0`.

Returns:: true if the condition was met, false otherwise.

void Gio::Socket::condition_wait ( Glib::IOCondition condition )

void Gio::Socket::connect	(	const Glib::RefPtr< SocketAddress >&	address,
		const Glib::RefPtr< Cancellable >&	cancellable
	)

Connect the socket to the specified remote address.

For connection oriented socket this generally means we attempt to make a connection to the address. For a connection-less socket it sets the default address for g_socket_send() and discards all incoming datagrams from other sources.

Generally connection oriented sockets can only connect once, but connection-less sockets can connect multiple times to change the default address.

If the connect call needs to do network I/O it will block, unless non-blocking I/O is enabled. Then IO_ERROR_PENDING is returned and the user can be notified of the connection finishing by waiting for the G_IO_OUT condition. The result of the connection can then be checked with g_socket_check_connect_result().

Since glibmm 2.22:

Parameters:

address	A SocketAddress specifying the remote address.
cancellable	A Cancellable or `0`.

Returns:: true if connected, false on error.

void Gio::Socket::connect ( const Glib::RefPtr< SocketAddress >& address )

static Glib::RefPtr<Socket> Gio::Socket::create	(	SocketFamily	family,
		SocketType	type,
		SocketProtocol	protocol,
		const Glib::RefPtr< Cancellable >&	cancellable = `Glib::RefPtr< Cancellable >()`
	)		`[static]`

Creates a new Socket with the defined family, type and protocol.

If protocol is 0 (SOCKET_PROTOCOL_DEFAULT) the default protocol type for the family and type is used.

The protocol is a family and type specific int that specifies what kind of protocol to use. SocketProtocol lists several common ones. Many families only support one protocol, and use 0 for this, others support several and using 0 means to use the default protocol for the family and type.

The protocol id is passed directly to the operating system, so you can use protocols not listed in SocketProtocol if you know the protocol number used for it.

Since glibmm 2.22:

Parameters:

family	The socket family to use, e.g. SOCKET_FAMILY_IPV4.
type	The socket type to use.
protocol	The id of the protocol to use, or 0 for default.

Returns:: A Socket or 0 on error. Free the returned object with Glib::object_unref().

Exceptions:

Glib::Error

static Glib::RefPtr<Socket> Gio::Socket::create_from_fd	(	int	fd,
		const Glib::RefPtr< Cancellable >&	cancellable = `Glib::RefPtr< Cancellable >()`
	)		`[static]`

Creates a new Socket from a native file descriptor or winsock SOCKET handle.

This reads all the settings from the file descriptor so that all properties should work. Note that the file descriptor will be set to non-blocking mode, independent on the blocking mode of the Socket.

Since glibmm 2.22:

Parameters:

fd	A native socket file descriptor.

Returns:: A Socket or 0 on error. Free the returned object with Glib::object_unref().

Exceptions:

Glib::Error

bool Gio::Socket::get_blocking ( ) const

Gets the blocking mode of the socket.

For details on blocking I/O, see g_socket_set_blocking().

Since glibmm 2.22:

Returns:: true if blocking I/O is used, false otherwise.

Glib::RefPtr<Credentials> Gio::Socket::get_credentials ( )

Returns the credentials of the foreign process connected to this socket, if any (e.g. it is only supported for SOCKET_FAMILY_UNIX sockets).

If this operation isn't supported on the OS, the method fails with the IO_ERROR_NOT_SUPPORTED error. On Linux this is implemented by reading the So::PEERCRED option on the underlying socket.

Other ways to obtain credentials from a foreign peer includes the UnixCredentialsMessage type and g_unix_connection_send_credentials() / g_unix_connection_receive_credentials() functions.

Since glibmm 2.26:

Returns:: 0 if error is set, otherwise a Credentials object that must be freed with Glib::object_unref().

Glib::RefPtr<const Credentials> Gio::Socket::get_credentials ( ) const

Returns the credentials of the foreign process connected to this socket, if any (e.g. it is only supported for SOCKET_FAMILY_UNIX sockets).

If this operation isn't supported on the OS, the method fails with the IO_ERROR_NOT_SUPPORTED error. On Linux this is implemented by reading the So::PEERCRED option on the underlying socket.

Other ways to obtain credentials from a foreign peer includes the UnixCredentialsMessage type and g_unix_connection_send_credentials() / g_unix_connection_receive_credentials() functions.

Since glibmm 2.26:

Returns:: 0 if error is set, otherwise a Credentials object that must be freed with Glib::object_unref().

SocketFamily Gio::Socket::get_family ( ) const

Gets the socket family of the socket.

Since glibmm 2.22:

Returns:: A SocketFamily.

int Gio::Socket::get_fd ( ) const

Returns the underlying OS socket object.

On unix this is a socket file descriptor, and on windows this is a Winsock2 SOCKET handle. This may be useful for doing platform specific or otherwise unusual operations on the socket.

Since glibmm 2.22:

Returns:: The file descriptor of the socket.

bool Gio::Socket::get_keepalive ( ) const

Gets the keepalive mode of the socket.

For details on this, see g_socket_set_keepalive().

Since glibmm 2.22:

Returns:: true if keepalive is active, false otherwise.

int Gio::Socket::get_listen_backlog ( ) const

Gets the listen backlog setting of the socket.

For details on this, see g_socket_set_listen_backlog().

Since glibmm 2.22:

Returns:: The maximum number of pending connections.

Glib::RefPtr<SocketAddress> Gio::Socket::get_local_address ( ) const

Try to get the local address of a bound socket.

This is only useful if the socket has been bound to a local address, either explicitly or implicitly when connecting.

Since glibmm 2.22:

Returns:: A SocketAddress or 0 on error. Free the returned object with Glib::object_unref().

SocketProtocol Gio::Socket::get_protocol ( ) const

Gets the socket protocol id the socket was created with.

In case the protocol is unknown, -1 is returned.

Since glibmm 2.22:

Returns:: A protocol id, or -1 if unknown.

Glib::RefPtr<SocketAddress> Gio::Socket::get_remote_address ( ) const

Try to get the remove address of a connected socket.

This is only useful for connection oriented sockets that have been connected.

Since glibmm 2.22:

Returns:: A SocketAddress or 0 on error. Free the returned object with Glib::object_unref().

SocketType Gio::Socket::get_socket_type ( ) const

Gets the socket type of the socket.

Since glibmm 2.22:

Returns:: A SocketType.

guint Gio::Socket::get_timeout ( ) const

Gets the timeout setting of the socket.

For details on this, see g_socket_set_timeout().

Since glibmm 2.26:

Returns:: The timeout in seconds.

const GSocket* Gio::Socket::gobj ( ) const [inline]

Provides access to the underlying C GObject.

Reimplemented from Gio::Initable.

GSocket* Gio::Socket::gobj ( ) [inline]

Provides access to the underlying C GObject.

Reimplemented from Gio::Initable.

GSocket* Gio::Socket::gobj_copy ( )

Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs.

bool Gio::Socket::is_closed ( )

Checks whether a socket is closed.

Since glibmm 2.22:

Returns:: true if socket is closed, false otherwise.

bool Gio::Socket::is_connected ( )

Check whether the socket is connected.

This is only useful for connection-oriented sockets.

Since glibmm 2.22:

Returns:: true if socket is connected, false otherwise.

void Gio::Socket::listen ( )

Marks the socket as a server socket, i.e. a socket that is used to accept incoming requests using g_socket_accept().

Before calling this the socket must be bound to a local address using g_socket_bind().

To set the maximum amount of outstanding clients, use g_socket_set_listen_backlog().

Since glibmm 2.22:

Returns:: true on success, false on error.

Glib::PropertyProxy<bool> Gio::Socket::property_blocking ( )

Whether or not I/O on this socket is blocking.