QLocalServer¶

PyQt5.QtNetwork.QLocalServer: Inherits from QObject.

Description¶

The QLocalServer class provides a local socket based server.

This class makes it possible to accept incoming local socket connections.

Call listen() to have the server start listening for incoming connections on a specified key. The newConnection signal is then emitted each time a client connects to the server.

Call nextPendingConnection() to accept the pending connection as a connected QLocalSocket. The function returns a pointer to a QLocalSocket that can be used for communicating with the client.

If an error occurs, serverError() returns the type of error, and errorString() can be called to get a human readable description of what happened.

When listening for connections, the name which the server is listening on is available through serverName().

Calling close() makes QLocalServer stop listening for incoming connections.

Although QLocalServer is designed for use with an event loop, it’s possible to use it without one. In that case, you must use waitForNewConnection(), which blocks until either a connection is available or a timeout expires.

See also

QLocalSocket, QTcpServer.

Classes¶

SocketOptions

Enums¶

SocketOption

This enum describes the possible options that can be used to create the socket. This changes the access permissions on platforms (Linux, Windows) that support access permissions on the socket. Both GroupAccess and OtherAccess may vary slightly in meanings depending on the platform.

See also

socketOptions().

Member	Value	Description
GroupAccessOption	0x2	Access is restricted to the same group but not the user that created the socket on Linux. Access is restricted to the primary group of the process on Windows
OtherAccessOption	0x4	Access is available to everyone but the user and group that created the socket on Linux. Access is available to everyone on Windows.
UserAccessOption	0x01	Access is restricted to the same user as the process that created the socket.
WorldAccessOption	0x7	No access restrictions.

Methods¶

__init__(parent: QObject = None): TODO

close(): Stop listening for incoming connections. Existing connections are not affected, but any new connections will be refused.

See also

isListening(), listen().

errorString() → str: Returns the human-readable message appropriate to the current error reported by serverError(). If no suitable string is available, an empty string is returned.

See also

serverError().

fullServerName() → str

Returns the full path that the server is listening on.

Note: This is platform specific

See also

listen(), serverName().

hasPendingConnections() → bool: Returns true if the server has a pending connection; otherwise returns false.

See also

nextPendingConnection(), setMaxPendingConnections().

incomingConnection(sip.voidptr)

This virtual function is called by QLocalServer when a new connection is available. socketDescriptor is the native socket descriptor for the accepted connection.

The base implementation creates a QLocalSocket, sets the socket descriptor and then stores the QLocalSocket in an internal list of pending connections. Finally newConnection is emitted.

Reimplement this function to alter the server’s behavior when a connection is available.

isListening() → bool: Returns true if the server is listening for incoming connections otherwise false.

See also

listen(), close().

listen(str) → bool

Tells the server to listen for incoming connections on name. If the server is currently listening then it will return false. Return true on success otherwise false.

name can be a single name and QLocalServer will determine the correct platform specific path. serverName() will return the name that is passed into listen.

Usually you would just pass in a name like “foo”, but on Unix this could also be a path such as “/tmp/foo” and on Windows this could be a pipe path such as “\.\pipe\foo”

Note: On Unix if the server crashes without closing listen will fail with AddressInUseError. To create a new server the file should be removed. On Windows two local servers can listen to the same pipe at the same time, but any connections will go to one of the server.

See also

serverName(), isListening(), close().

listen(sip.voidptr) → bool: TODO

maxPendingConnections() → int: Returns the maximum number of pending accepted connections. The default is 30.

See also

setMaxPendingConnections(), hasPendingConnections().

nextPendingConnection() → QLocalSocket

Returns the next pending connection as a connected QLocalSocket object.

The socket is created as a child of the server, which means that it is automatically deleted when the QLocalServer object is destroyed. It is still a good idea to delete the object explicitly when you are done with it, to avoid wasting memory.

0 is returned if this function is called when there are no pending connections.

@staticmethod removeServer(str) → bool

Removes any server instance that might cause a call to listen() to fail and returns true if successful; otherwise returns false. This function is meant to recover from a crash, when the previous server instance has not been cleaned up.

On Windows, this function does nothing; on Unix, it removes the socket file given by name.

Warning: Be careful to avoid removing sockets of running instances.

serverError() → SocketError: Returns the type of error that occurred last or NoError.

See also

errorString().

serverName() → str: Returns the server name if the server is listening for connections; otherwise returns QString()

See also

listen(), fullServerName().

setMaxPendingConnections(int)

Sets the maximum number of pending accepted connections to numConnections. QLocalServer will accept no more than numConnections incoming connections before nextPendingConnection() is called.

Note: Even though QLocalServer will stop accepting new connections after it has reached its maximum number of pending connections, the operating system may still keep them in queue which will result in clients signaling that it is connected.

setSocketOptions(Union[SocketOptions, SocketOption]): TODO

socketDescriptor() → sip.voidptr

Returns the native socket descriptor the server uses to listen for incoming instructions, or -1 if the server is not listening.

The type of the descriptor depends on the platform:

On Windows, the returned value is a Winsock 2 Socket Handle.
With WinRT and on INTEGRITY, the returned value is the QTcpServer socket descriptor and the type is defined by socketDescriptor().
On all other UNIX-like operating systems, the type is a file descriptor representing a listening socket.

See also

listen().

socketOptions() → SocketOptions: Returns the socket options set on the socket.

See also

setSocketOptions().

waitForNewConnection(msecs: int = 0) → (bool, bool)

Waits for at most msec milliseconds or until an incoming connection is available. Returns true if a connection is available; otherwise returns false. If the operation timed out and timedOut is not 0, *timedOut will be set to true.

This is a blocking function call. Its use is ill-advised in a single-threaded GUI application, since the whole application will stop responding until the function returns. is mostly useful when there is no event loop available.

The non-blocking alternative is to connect to the newConnection signal.

If msec is -1, this function will not time out.

Signals¶

newConnection(): TODO