QLocalServer

The QLocalServer class provides a local socket based server. More…

Synopsis

Functions

• def close ()

• def errorString ()

• def fullServerName ()

• def isListening ()

• def listen (name)

• def listen (socketDescriptor)

• def maxPendingConnections ()

• def serverError ()

• def serverName ()

• def setMaxPendingConnections (numConnections)

• def setSocketOptions (options)

• def socketDescriptor ()

• def socketOptions ()

• def waitForNewConnection (msec)

Virtual functions

• def hasPendingConnections ()

• def incomingConnection (socketDescriptor)

• def nextPendingConnection ()

Signals

• def newConnection ()

Static functions

• def removeServer (name)

Detailed Description

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

class PySide2.QtNetwork.QLocalServer([parent=None])

param parent:

PySide2.QtCore.QObject

Create a new local socket server with the given parent .

See also

listen()

PySide2.QtNetwork.QLocalServer.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.

Constant	Description
QLocalServer.NoOptions	No access restrictions have been set.
QLocalServer.UserAccessOption	Access is restricted to the same user as the process that created the socket.
QLocalServer.GroupAccessOption	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
QLocalServer.OtherAccessOption	Access is available to everyone but the user and group that created the socket on Linux. Access is available to everyone on Windows.
QLocalServer.WorldAccessOption	No access restrictions.

See also

socketOptions

PySide2.QtNetwork.QLocalServer.close()

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

See also

isListening() listen()

PySide2.QtNetwork.QLocalServer.errorString()

Return type:

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()

PySide2.QtNetwork.QLocalServer.fullServerName()

Return type:

str

Returns the full path that the server is listening on.

Note: This is platform specific

See also

listen() serverName()

PySide2.QtNetwork.QLocalServer.hasPendingConnections()

Return type:

bool

Returns true if the server has a pending connection; otherwise returns false .

See also

nextPendingConnection() setMaxPendingConnections()

PySide2.QtNetwork.QLocalServer.incomingConnection(socketDescriptor)

Parameters:

socketDescriptor – quintptr

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.

See also

newConnection() nextPendingConnection() setSocketDescriptor()

PySide2.QtNetwork.QLocalServer.isListening()

Return type:

bool

Returns true if the server is listening for incoming connections otherwise false.

See also

listen() close()

PySide2.QtNetwork.QLocalServer.listen(name)

Parameters:

name – str

Return type:

bool

PySide2.QtNetwork.QLocalServer.listen(socketDescriptor)

Parameters:

socketDescriptor – qintptr

Return type:

bool

Instructs the server to listen for incoming connections on socketDescriptor . The property returns false if the server is currently listening. It returns true on success; otherwise, it returns false . The socket must be ready to accept new connections with no extra platform-specific functions called. The socket is set into non-blocking mode.

serverName() , fullServerName() may return a string with a name if this option is supported by the platform; otherwise, they return an empty QString .

See also

isListening() close()

PySide2.QtNetwork.QLocalServer.maxPendingConnections()

Return type:

int

Returns the maximum number of pending accepted connections. The default is 30.

See also

setMaxPendingConnections() hasPendingConnections()

PySide2.QtNetwork.QLocalServer.newConnection()

PySide2.QtNetwork.QLocalServer.nextPendingConnection()

Return type:

PySide2.QtNetwork.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.

None is returned if this function is called when there are no pending connections.

See also

hasPendingConnections() newConnection() incomingConnection()

static PySide2.QtNetwork.QLocalServer.removeServer(name)

Parameters:

name – str

Return type:

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.

PySide2.QtNetwork.QLocalServer.serverError()

Return type:

SocketError

Returns the type of error that occurred last or NoError .

See also

errorString()

PySide2.QtNetwork.QLocalServer.serverName()

Return type:

str

Returns the server name if the server is listening for connections; otherwise returns QString()

See also

listen() fullServerName()

PySide2.QtNetwork.QLocalServer.setMaxPendingConnections(numConnections)

Parameters:

numConnections – 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.

See also

maxPendingConnections() hasPendingConnections()

PySide2.QtNetwork.QLocalServer.setSocketOptions(options)

Parameters:

options – SocketOptions

The method controls how the socket operates. For example the socket may restrict access to what user ids can connect to the socket.

These options must be set before listen() is called.

In some cases, such as with Unix domain sockets on Linux, the access to the socket will be determined by file system permissions, and are created based on the umask. Setting the access flags will override this and will restrict or permit access as specified.

Other Unix-based operating systems, such as macOS, do not honor file permissions for Unix domain sockets and by default have WorldAccess and these permission flags will have no effect.

On Windows, UserAccessOption is sufficient to allow a non elevated process to connect to a local server created by an elevated process run by the same user. GroupAccessOption refers to the primary group of the process (see TokenPrimaryGroup in the Windows documentation). OtherAccessOption refers to the well known “Everyone” group.

By default none of the flags are set, access permissions are the platform default.

See also

listen()

PySide2.QtNetwork.QLocalServer.socketDescriptor()

Return type:

qintptr

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()

PySide2.QtNetwork.QLocalServer.socketOptions()

Return type:

SocketOptions

The method controls how the socket operates. For example the socket may restrict access to what user ids can connect to the socket.

These options must be set before listen() is called.

In some cases, such as with Unix domain sockets on Linux, the access to the socket will be determined by file system permissions, and are created based on the umask. Setting the access flags will override this and will restrict or permit access as specified.

Other Unix-based operating systems, such as macOS, do not honor file permissions for Unix domain sockets and by default have WorldAccess and these permission flags will have no effect.

On Windows, UserAccessOption is sufficient to allow a non elevated process to connect to a local server created by an elevated process run by the same user. GroupAccessOption refers to the primary group of the process (see TokenPrimaryGroup in the Windows documentation). OtherAccessOption refers to the well known “Everyone” group.

By default none of the flags are set, access permissions are the platform default.

See also

listen()

PySide2.QtNetwork.QLocalServer.waitForNewConnection(msec)

Parameters:

msec – int

Return type:

(retval, timeOut)

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 None , *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.

See also

hasPendingConnections() nextPendingConnection()