Pyqt；QTcpSocket在服务器重启后总是处于连接状态；

Question

我有一个 QTcpSocket 的子类。问题是：当我第一次连接到服务器时，一切正常。但是在套接字连接后，我重启服务器（用 Python 写的 socketServer，只是关闭然后重新启动脚本），套接字断开连接并尝试在服务器关闭时重新连接。但是当我再次启动服务器时，什么也没发生，套接字的状态一直显示为 ConnectingState（连接中）……这到底是怎么回事？

这里是示例代码：

# -*- coding: utf-8 -*-
from PyQt4.QtCore import QVariant,  QTimer, pyqtSignal, QCoreApplication
import sys
from PyQt4.QtNetwork import QTcpSocket
from re import match
import json

MAX_WAIT_LEN  = 8

class UpQSocket(QTcpSocket):
    data_ready = pyqtSignal(unicode)
    def __init__(self):
        QTcpSocket.__init__(self)
        self.wait_len = ''
        self.temp = ''
        self.setSocketOption(QTcpSocket.KeepAliveOption, QVariant(1))
        self.readyRead.connect(self.on_ready_read)
        self.connected.connect(self.on_connected)
        self.disconnected.connect(self.on_disconnect)
        self.error.connect(self.on_error)
        self.data_ready.connect(self.print_command)

    def connectToHost(self, host, port):
        print 'connectToHost'
        self.temp = ''
        self.wait_len = ''
        QTcpSocket.abort(self)
        QTcpSocket.connectToHost(self, host, port)

    def close(self):
        print 'close!'
        self.disconnectFromHost()

    def send(self, data):
        self.writeData('%s|%s' % (len(data), data))

    def on_ready_read(self):
        if self.bytesAvailable():
            data = str(self.readAll())
            while data:
                if not self.wait_len and '|' in data:#new data and new message
                    self.wait_len , data = data.split('|',1)
                    if match('[0-9]+', self.wait_len) and (len(self.wait_len) <= MAX_WAIT_LEN) and data.startswith('{'):#okay, this is normal length
                        self.wait_len = int(self.wait_len)
                        self.temp = data[:self.wait_len]
                        data = data[self.wait_len:]
                    else:#oh, it was crap
                        self.wait_len , self.temp = '',''
                        return
                elif self.wait_len:#okay, not new message, appending
                    tl= int(self.wait_len)-len(self.temp)
                    self.temp+=data[:tl]
                    data=data[tl:]
                elif not self.wait_len and not '|' in data:#crap
                    return
                if self.wait_len and self.wait_len == len(self.temp):#okay, full message
                    self.data_ready.emit(self.temp)
                    self.wait_len , self.temp = '',''
                    if not data:
                        return

    def print_command(self,data):
        print 'data!'

    def get_sstate(self):
        print self.state()

    def on_error(self):
        print 'error', self.errorString()
        self.close()
        self.connectToHost('dev.ulab.ru', 10000)

    def on_disconnect(self):
        print 'disconnected!'

    def on_connected(self):
        print 'connected!'
        self.send(json.dumps(
                {'command' : "operator_insite",
                 'password' : "376c43878878ac04e05946ec1dd7a55f",
                 'login' : "nsandr",
                 'version':unicode("1.2.9")}))

if __name__ == "__main__":
    app = QCoreApplication(sys.argv)
    main_socket = UpQSocket()
    state_timer = QTimer()
    state_timer.setInterval(1000)
    state_timer.timeout.connect(main_socket.get_sstate)
    state_timer.start()
    main_socket.connectToHost('dev.ulab.ru', 10000)
    sys.exit(app.exec_())

这是输出结果：

    connectToHost
    1
    1
connected!
data!
data!
3
3
3
3
3
error The remote host closed the connection 
close!
disconnected!
connectToHost
2
2

Answer 1

解决方法：

import functools

def on_error(self):
    print 'error', self.errorString()
    QTimer.singleShot(2000, functools.partial(self.connectToHost, 'localhost', 9999))
    # 2000 - your prefered reconnect timeout in ms

更新

在Qt的错误报告评论中，有一个更正确的解决方案，链接在这里：QTBUG-18082。这里是Python的实现：

@QtCore.pyqtSlot()
def do_reconnect(self):
    print 'Trying to reconnect'
    self.connectToHost('localhost', 9999)

def on_error(self):
    print 'error', self.errorString()
    QtCore.QMetaObject.invokeMethod(self, 'do_reconnect',  QtCore.Qt.QueuedConnection)

或者直接：

QTimer.singleShot(0, self.do_reconnect) # or any callable, slot is unnecessary 

无论如何，这都会调用 QtCore.QMetaObject.invokeMethod，并使用 QueuedConnection 连接类型 (来源)