realpython / realpython/materials

Socket with if-loops does not give a consistent result

Open
#37 1 comment 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Dominant language
Jupyter Notebook
Stars
5.2k
Forks
5.3k
Avg merge
4d 10h
Merged PRs (30d)
10

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:

  1. 1st time click on button ---> Checked & if part run [working]
  2. 2nd time click on button ---> Unchecked & else part run [working]
  3. 3rd time click on button ---> again it Checked [here it checked but my program hangs & not receiving the data from sender computer]

Contributor guide

No contributing guide indexed for this repository

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. 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

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.