QLocalSocket

The QLocalSocket class provides a local socket. More

Inheritance diagram of PySide2.QtNetwork.QLocalSocket

Synopsis

Functions

Signals

Detailed Description

On Windows this is a named pipe and on Unix this is a local domain socket.

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

Although QLocalSocket is designed for use with an event loop, it’s possible to use it without one. In that case, you must use waitForConnected() , waitForReadyRead() , waitForBytesWritten() , and waitForDisconnected() which blocks until the operation is complete or the timeout expires.

See also

QLocalServer

class QLocalSocket([parent=None])
param parent

QObject

Creates a new local socket. The parent argument is passed to QObject ‘s constructor.

PySide2.QtNetwork.QLocalSocket.LocalSocketError

The LocalServerError enumeration represents the errors that can occur. The most recent error can be retrieved through a call to error() .

Constant

Description

QLocalSocket.ConnectionRefusedError

The connection was refused by the peer (or timed out).

QLocalSocket.PeerClosedError

The remote socket closed the connection. Note that the client socket (i.e., this socket) will be closed after the remote close notification has been sent.

QLocalSocket.ServerNotFoundError

The local socket name was not found.

QLocalSocket.SocketAccessError

The socket operation failed because the application lacked the required privileges.

QLocalSocket.SocketResourceError

The local system ran out of resources (e.g., too many sockets).

QLocalSocket.SocketTimeoutError

The socket operation timed out.

QLocalSocket.DatagramTooLargeError

The datagram was larger than the operating system’s limit (which can be as low as 8192 bytes).

QLocalSocket.ConnectionError

An error occurred with the connection.

QLocalSocket.UnsupportedSocketOperationError

The requested socket operation is not supported by the local operating system.

QLocalSocket.OperationError

An operation was attempted while the socket was in a state that did not permit it.

QLocalSocket.UnknownSocketError

An unidentified error occurred.

PySide2.QtNetwork.QLocalSocket.LocalSocketState

This enum describes the different states in which a socket can be.

Constant

Description

QLocalSocket.UnconnectedState

The socket is not connected.

QLocalSocket.ConnectingState

The socket has started establishing a connection.

QLocalSocket.ConnectedState

A connection is established.

QLocalSocket.ClosingState

The socket is about to close (data may still be waiting to be written).

See also

state()

PySide2.QtNetwork.QLocalSocket.abort()

Aborts the current connection and resets the socket. Unlike disconnectFromServer() , this function immediately closes the socket, clearing any pending data in the write buffer.

See also

disconnectFromServer() close()

PySide2.QtNetwork.QLocalSocket.connectToServer([openMode=QIODevice.ReadWrite])
Parameters

openModeOpenMode

Attempts to make a connection to serverName() . setServerName() must be called before you open the connection. Alternatively you can use (const QString &name, OpenMode openMode );

The socket is opened in the given openMode and first enters ConnectingState . If a connection is established, QLocalSocket enters ConnectedState and emits connected() .

After calling this function, the socket can emit error() to signal that an error occurred.

PySide2.QtNetwork.QLocalSocket.connectToServer(name[, openMode=QIODevice.ReadWrite])
Parameters
  • name – unicode

  • openModeOpenMode

This is an overloaded function.

Set the server name and attempts to make a connection to it.

The socket is opened in the given openMode and first enters ConnectingState . If a connection is established, QLocalSocket enters ConnectedState and emits connected() .

After calling this function, the socket can emit error() to signal that an error occurred.

PySide2.QtNetwork.QLocalSocket.connected()
PySide2.QtNetwork.QLocalSocket.disconnectFromServer()

Attempts to close the socket. If there is pending data waiting to be written, QLocalSocket will enter ClosingState and wait until all data has been written. Eventually, it will enter UnconnectedState and emit the disconnectedFromServer() signal.

PySide2.QtNetwork.QLocalSocket.disconnected()
PySide2.QtNetwork.QLocalSocket.error()
Return type

LocalSocketError

Returns the type of error that last occurred.

See also

state() errorString()

PySide2.QtNetwork.QLocalSocket.error(socketError)
Parameters

socketErrorLocalSocketError

PySide2.QtNetwork.QLocalSocket.flush()
Return type

bool

This function writes as much as possible from the internal write buffer to the socket, without blocking. If any data was written, this function returns true ; otherwise false is returned.

Call this function if you need QLocalSocket to start sending buffered data immediately. The number of bytes successfully written depends on the operating system. In most cases, you do not need to call this function, because QLocalSocket will start sending data automatically once control goes back to the event loop. In the absence of an event loop, call waitForBytesWritten() instead.

See also

write() waitForBytesWritten()

PySide2.QtNetwork.QLocalSocket.fullServerName()
Return type

unicode

Returns the server path that the socket is connected to.

Note

The return value of this function is platform specific.

PySide2.QtNetwork.QLocalSocket.isValid()
Return type

bool

Returns true if the socket is valid and ready for use; otherwise returns false .

Note

The socket’s state must be ConnectedState before reading and writing can occur.

PySide2.QtNetwork.QLocalSocket.readBufferSize()
Return type

qint64

Returns the size of the internal read buffer. This limits the amount of data that the client can receive before you call read() or readAll() . A read buffer size of 0 (the default) means that the buffer has no size limit, ensuring that no data is lost.

See also

setReadBufferSize() read()

PySide2.QtNetwork.QLocalSocket.serverName()
Return type

unicode

Returns the name of the peer as specified by setServerName() , or an empty QString if setServerName() has not been called or connectToServer() failed.

PySide2.QtNetwork.QLocalSocket.setReadBufferSize(size)
Parameters

sizeqint64

Sets the size of QLocalSocket ‘s internal read buffer to be size bytes.

If the buffer size is limited to a certain size, QLocalSocket won’t buffer more than this size of data. Exceptionally, a buffer size of 0 means that the read buffer is unlimited and all incoming data is buffered. This is the default.

This option is useful if you only read the data at certain points in time (e.g., in a real-time streaming application) or if you want to protect your socket against receiving too much data, which may eventually cause your application to run out of memory.

See also

readBufferSize() read()

PySide2.QtNetwork.QLocalSocket.setServerName(name)
Parameters

name – unicode

Set the name of the peer to connect to. On Windows name is the name of a named pipe; on Unix name is the name of a local domain socket.

This function must be called when the socket is not connected.

See also

serverName()

PySide2.QtNetwork.QLocalSocket.setSocketDescriptor(socketDescriptor[, socketState=ConnectedState[, openMode=QIODevice.ReadWrite]])
Parameters
  • socketDescriptorqintptr

  • socketStateLocalSocketState

  • openModeOpenMode

Return type

bool

Initializes QLocalSocket with the native socket descriptor socketDescriptor . Returns true if socketDescriptor is accepted as a valid socket descriptor; otherwise returns false . The socket is opened in the mode specified by openMode , and enters the socket state specified by socketState .

Note

It is not possible to initialize two local sockets with the same native socket descriptor.

See also

socketDescriptor() state() openMode()

PySide2.QtNetwork.QLocalSocket.socketDescriptor()
Return type

qintptr

Returns the native socket descriptor of the QLocalSocket object if this is available; otherwise returns -1.

The socket descriptor is not available when QLocalSocket is in UnconnectedState . 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 QTcpSocket socket descriptor and the type is defined by socketDescriptor .

  • On all other UNIX-like operating systems, the type is a file descriptor representing a socket.

PySide2.QtNetwork.QLocalSocket.state()
Return type

LocalSocketState

Returns the state of the socket.

See also

error()

PySide2.QtNetwork.QLocalSocket.stateChanged(socketState)
Parameters

socketStateLocalSocketState

PySide2.QtNetwork.QLocalSocket.waitForConnected([msecs=30000])
Parameters

msecsint

Return type

bool

Waits until the socket is connected, up to msecs milliseconds. If the connection has been established, this function returns true ; otherwise it returns false . In the case where it returns false , you can call error() to determine the cause of the error.

The following example waits up to one second for a connection to be established:

socket.connectToServer("market")
if (socket.waitForConnected(1000))
    print("Connected!")

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

PySide2.QtNetwork.QLocalSocket.waitForDisconnected([msecs=30000])
Parameters

msecsint

Return type

bool

Waits until the socket has disconnected, up to msecs milliseconds. If the connection has been disconnected, this function returns true ; otherwise it returns false . In the case where it returns false , you can call error() to determine the cause of the error.

The following example waits up to one second for a connection to be closed:

socket.disconnectFromServer()
if (socket.waitForDisconnected(1000))
    print("Disconnected!")

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

See also

disconnectFromServer() close()