realpython / realpython/materials
Socket with if-loops does not give a consistent result
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Description
The program is continuously receiving data from the sender side. And I have a checked/unchecked button when I make it checked it runs the if part...that's good. Now I make it unchecked then else part runs and prints Unchecked going to close socket, so that's also good.
The problem is when I am going to make it again checked (2nd time) to run if part again it just print Checked and my program hangs. Why is this happening? It should receive the data but it hangs. Please tell me the solution.
def show_markers(self):
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = socket.gethostbyname('192.168.225.12')
s.connect((host, port))
scale=0
while True:
if self.iconAction.isChecked():
print ('Checked')
m = QgsVertexMarker(self.iface.mapCanvas())
data = s.recv(SIZE)
data1 = s.recv(SIZE)
c = data.decode()
d = data1.decode()
x = float(c)
y = float(d)
print("printing X :", x)
print("printing Y :", y)
rect = QgsRectangle(float(x)-scale, float(y)-scale, float(x)+scale, float(y)+scale)
me = self.iface.mapCanvas()
me.setExtent(rect)
me.refresh()
m.setCenter(QgsPointXY(x, y))
m.setColor(QColor(255, 0, 0))
m.setIconSize(7)
m.setIconType(QgsVertexMarker.ICON_X) # or ICON_CROSS, ICON_X
m.setPenWidth(3)
else:
print('Unchecked going to close socket')
s.shutdown(10)
s.close()
I am assuming it should work like:
- 1st time click on button ---> Checked & if part run [working]
- 2nd time click on button ---> Unchecked & else part run [working]
- 3rd time click on button ---> again it Checked [here it checked but my program hangs & not receiving the data from sender computer]
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First steps
- Read the whole issue, then the project's contributing guide.
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- Open a pull request that references the issue number.
Research direction
Start at the show_markers entry point and trace the loop around the checkbox state, recv calls, and socket shutdown/close paths. Reproduce the three-toggle sequence, then verify that returning to the checked state receives data without hanging and that the socket lifecycle remains valid.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- desktop, networking
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 25/100