python3+PyQt5 Create Multithreaded Network Application TCP Client and TCP Server Instances

This article re-implements a multi-threaded server based on the above.

The following is the program code for the TCP client:

#!/usr/bin/env python3

import sys
from PyQt5.QtCore import (QByteArray, QDataStream, QDate, QIODevice,
    QRegExp, Qt)
from PyQt5.QtWidgets import (QApplication, QDateEdit, QFrame, QGridLayout,
    QHBoxLayout, QLabel, QLineEdit, QPushButton,
    QWidget)
from PyQt5.QtGui import QRegExpValidator
from PyQt5.QtNetwork import (QTcpSocket,)

MAC = True
try:
  from PyQt5.QtGui import qt_mac_set_native_menubar
except ImportError:
  MAC = False

PORT = 9407
SIZEOF_UINT16 = 2


class BuildingServicesClient(QWidget):

  def __init__(self, parent=None):
    super(BuildingServicesClient, self).__init__(parent)

    self.socket = QTcpSocket()
    self.nextBlockSize = 0
    self.request = None

    roomLabel = QLabel("&Room")
    self.roomEdit = QLineEdit()
    roomLabel.setBuddy(self.roomEdit)
    regex = QRegExp(r"[0-9](?:0[1-9]|[12][0-9]|3[0-4])")
    self.roomEdit.setValidator(QRegExpValidator(regex, self))
    self.roomEdit.setAlignment(Qt.AlignRight|Qt.AlignVCenter)
    dateLabel = QLabel("&Date")
    self.dateEdit = QDateEdit()
    dateLabel.setBuddy(self.dateEdit)
    self.dateEdit.setAlignment(Qt.AlignRight|Qt.AlignVCenter)
    self.dateEdit.setDate(QDate.currentDate().addDays(1))
    self.dateEdit.setDisplayFormat("yyyy-MM-dd")
    responseLabel = QLabel("Response")
    self.responseLabel = QLabel()
    self.responseLabel.setFrameStyle(QFrame.StyledPanel|QFrame.Sunken)

    self.bookButton = QPushButton("&Book")
    self.bookButton.setEnabled(False)
    self.unBookButton = QPushButton("&Unbook")
    self.unBookButton.setEnabled(False)
    quitButton = QPushButton("&Quit")
    if not MAC:
      self.bookButton.setFocusPolicy(Qt.NoFocus)
      self.unBookButton.setFocusPolicy(Qt.NoFocus)

    buttonLayout = QHBoxLayout()
    buttonLayout.addWidget(self.bookButton)
    buttonLayout.addWidget(self.unBookButton)
    buttonLayout.addStretch()
    buttonLayout.addWidget(quitButton)
    layout = QGridLayout()
    layout.addWidget(roomLabel, 0, 0)
    layout.addWidget(self.roomEdit, 0, 1)
    layout.addWidget(dateLabel, 0, 2)
    layout.addWidget(self.dateEdit, 0, 3)
    layout.addWidget(responseLabel, 1, 0)
    layout.addWidget(self.responseLabel, 1, 1, 1, 3)
    layout.addLayout(buttonLayout, 2, 1, 1, 4)
    self.setLayout(layout)

    self.socket.connected.connect(self.sendRequest)
    self.socket.readyRead.connect(self.readResponse)
    self.socket.disconnected.connect(self.serverHasStopped)
    #self.connect(self.socket,
    #       SIGNAL("error(QAbstractSocket::SocketError)"),
     #      self.serverHasError)
    self.socket.error.connect(self.serverHasError)
    self.roomEdit.textEdited.connect(self.updateUi)
    self.dateEdit.dateChanged.connect(self.updateUi)

    self.bookButton.clicked.connect(self.book)
    self.unBookButton.clicked.connect(self.unBook)
    quitButton.clicked.connect(self.close)

    self.setWindowTitle("Building Services")


  def updateUi(self):
    enabled = False
    if (self.roomEdit.text() and
      self.dateEdit.date() > QDate.currentDate()):
      enabled = True
    if self.request is not None:
      enabled = False
    self.bookButton.setEnabled(enabled)
    self.unBookButton.setEnabled(enabled)


  def closeEvent(self, event):
    self.socket.close()
    event.accept()


  def book(self):
    self.issueRequest("BOOK", self.roomEdit.text(),
             self.dateEdit.date())


  def unBook(self):
    self.issueRequest("UNBOOK", self.roomEdit.text(),
             self.dateEdit.date())


  def issueRequest(self, action, room, date):
    self.request = QByteArray()
    stream = QDataStream(self.request, QIODevice.WriteOnly)
    stream.setVersion(QDataStream.Qt_5_7)
    stream.writeUInt16(0)
    stream.writeQString(action)
    stream.writeQString(room)
    stream << date
    stream.device().seek(0)
    stream.writeUInt16(self.request.size() - SIZEOF_UINT16)#overwrite seek(0)
    self.updateUi()
    if self.socket.isOpen():
      self.socket.close()
    self.responseLabel.setText("Connecting to server...")
    self.socket.connectToHost("localhost", PORT)


  def sendRequest(self):
    self.responseLabel.setText("Sending request...")
    self.nextBlockSize = 0
    self.socket.write(self.request)
    self.request = None


  def readResponse(self):
    stream = QDataStream(self.socket)
    stream.setVersion(QDataStream.Qt_5_7)

    while True:
      if self.nextBlockSize == 0:
        if self.socket.bytesAvailable() < SIZEOF_UINT16:
          break
        self.nextBlockSize = stream.readUInt16()
      if self.socket.bytesAvailable() < self.nextBlockSize:
        break
      action = ""
      room = ""
      date = QDate()
      #stream >> action >> room
      action=stream.readQString()
      room=stream.readQString()
      if action != "ERROR":
        stream >> date
      if action == "ERROR":
        msg = "Error: {0}".format(room)
      elif action == "BOOK":
        msg = "Booked room {0} for {1}".format(room,date.toString(Qt.ISODate))
      elif action == "UNBOOK":
        msg = "Unbooked room {0} for {1}".format(room,date.toString(Qt.ISODate))
      self.responseLabel.setText(msg)
      self.updateUi()
      self.nextBlockSize = 0


  def serverHasStopped(self):
    self.responseLabel.setText(
        "Error: Connection closed by server")
    self.socket.close()


  def serverHasError(self, error):
    self.responseLabel.setText("Error: {0}".format(self.socket.errorString()))
    self.socket.close()


app = QApplication(sys.argv)
form = BuildingServicesClient()
form.show()
app.exec_()

The following is the program code for the TCP server:

#!/usr/bin/env python3
import bisect
import collections
import sys
from PyQt5.QtCore import (QByteArray, QDataStream, QDate, QReadWriteLock, QThread,QIODevice, Qt)
from PyQt5.QtWidgets import (QApplication, QMessageBox, QPushButton)
from PyQt5.QtNetwork import (QAbstractSocket,QHostAddress, QTcpServer, QTcpSocket)

PORT = 9407
SIZEOF_UINT16 = 2
MAX_BOOKINGS_PER_DAY = 5

# Key = date, value = list of room IDs
Bookings = collections.defaultdict(list)


def printBookings():
  for key in sorted(Bookings):
    print(key, Bookings[key])
  print()


class Thread(QThread):

  lock = QReadWriteLock()

  def __init__(self, socketId, parent):
    super(Thread, self).__init__(parent)
    self.socketId = socketId


  def run(self):
    socket = QTcpSocket()
    if not socket.setSocketDescriptor(self.socketId):
      #self.emit(SIGNAL("error(int)"), socket.error())
      self.error.connect(socket.error)
      return
    while socket.state() == QAbstractSocket.ConnectedState:
      nextBlockSize = 0
      stream = QDataStream(socket)
      stream.setVersion(QDataStream.Qt_5_7)
      if (socket.waitForReadyRead() and
        socket.bytesAvailable() >= SIZEOF_UINT16):
        nextBlockSize = stream.readUInt16()
      else:
        self.sendError(socket, "Cannot read client request")
        return
      if socket.bytesAvailable() < nextBlockSize:
        if (not socket.waitForReadyRead(60000) or
          socket.bytesAvailable() < nextBlockSize):
          self.sendError(socket, "Cannot read client data")
          return
      action = ""
      room = ""
      date = QDate()
      action=stream.readQString()
      if action in ("BOOK", "UNBOOK"):
        room=stream.readQString()
        stream >> date
        try:
          Thread.lock.lockForRead()
          bookings = Bookings.get(date.toPyDate())
        finally:
          Thread.lock.unlock()
        uroom = str(room)
      if action == "BOOK":
        newlist = False
        try:
          Thread.lock.lockForRead()
          if bookings is None:
            newlist = True
        finally:
          Thread.lock.unlock()
        if newlist:
          try:
            Thread.lock.lockForWrite()
            bookings = Bookings[date.toPyDate()]
          finally:
            Thread.lock.unlock()
        error = None
        insert = False
        try:
          Thread.lock.lockForRead()
          if len(bookings) < MAX_BOOKINGS_PER_DAY:
            if uroom in bookings:
              error = "Cannot accept duplicate booking"
            else:
              insert = True
          else:
            error = "{0} is fully booked".format(date.toString(Qt.ISODate))
        finally:
          Thread.lock.unlock()
        if insert:
          try:
            Thread.lock.lockForWrite()
            bisect.insort(bookings, uroom)
          finally:
            Thread.lock.unlock()
          self.sendReply(socket, action, room, date)
        else:
          self.sendError(socket, error)
      elif action == "UNBOOK":
        error = None
        remove = False
        try:
          Thread.lock.lockForRead()
          if bookings is None or uroom not in bookings:
            error = "Cannot unbook nonexistent booking"
          else:
            remove = True
        finally:
          Thread.lock.unlock()
        if remove:
          try:
            Thread.lock.lockForWrite()
            bookings.remove(uroom)
          finally:
            Thread.lock.unlock()
          self.sendReply(socket, action, room, date)
        else:
          self.sendError(socket, error)
      else:
        self.sendError(socket, "Unrecognized request")
      socket.waitForDisconnected()
      try:
        Thread.lock.lockForRead()
        printBookings()
      finally:
        Thread.lock.unlock()


  def sendError(self, socket, msg):
    reply = QByteArray()
    stream = QDataStream(reply, QIODevice.WriteOnly)
    stream.setVersion(QDataStream.Qt_5_7)
    stream.writeUInt16(0)
    stream.writeQString("ERROR")
    stream.writeQString(msg)
    stream.device().seek(0)
    stream.writeUInt16(reply.size() - SIZEOF_UINT16)
    socket.write(reply)

  def sendReply(self, socket, action, room, date):
    reply = QByteArray()
    stream = QDataStream(reply, QIODevice.WriteOnly)
    stream.setVersion(QDataStream.Qt_5_7)
    stream.writeUInt16(0)
    stream.writeQString(action)
    stream.writeQString(room)
    stream<<date
    stream.device().seek(0)
    stream.writeUInt16(reply.size() - SIZEOF_UINT16)
    socket.write(reply)

class TcpServer(QTcpServer):

  def __init__(self, parent=None):
    super(TcpServer, self).__init__(parent)


  def incomingConnection(self, socketId):
    thread = Thread(socketId, self)
    #self.connect(thread, SIGNAL("finished()"),
    #       thread, SLOT("deleteLater()"))
    thread.finished.connect(thread.deleteLater)
    thread.start()


class BuildingServicesDlg(QPushButton):

  def __init__(self, parent=None):
    super(BuildingServicesDlg, self).__init__(
        "&Close Server", parent)
    self.setWindowFlags(Qt.WindowStaysOnTopHint)

    self.loadBookings()
    self.tcpServer = TcpServer(self)
    if not self.tcpServer.listen(QHostAddress("0.0.0.0"), PORT):
      QMessageBox.critical(self, "Building Services Server","Failed to start server: {0}".format(self.tcpServer.errorString()))
      self.close()
      return

    self.clicked.connect(self.close)
    font = self.font()
    font.setPointSize(24)
    self.setFont(font)
    self.setWindowTitle("Building Services Server")


  def loadBookings(self):
    # Generate fake data
    import random

    today = QDate.currentDate()
    for i in range(10):
      date = today.addDays(random.randint(7, 60))
      for j in range(random.randint(1, MAX_BOOKINGS_PER_DAY)):
        # Rooms are 001..534 excl. 100, 200, ..., 500
        floor = random.randint(0, 5)
        room = random.randint(1, 34)
        bookings = Bookings[date.toPyDate()]
        if len(bookings) >= MAX_BOOKINGS_PER_DAY:
          continue
        bisect.insort(bookings, "{0:1d}{1:02d}".format(
               floor, room))
    printBookings()


app = QApplication(sys.argv)
form = BuildingServicesDlg()
form.show()
form.move(0, 0)
app.exec_()