Something is wrong with the Message when running the demo

[pylpyl]

• Operating System: Ubuntu 20.04
• UE4 Version: 4.5
• UnrealCV Version: 0.4.0
• Client (python2, 3 or matlab): python 2.7
• Problem Description:

I installed the unrealcv and tried to run the demos.
First, I started the RealisticRendering game with ./playground. Then I ran the following code:

from unrealcv import client
client.connect() # Connect to the game
if not client.isconnected(): # Check if the connection is successfully established
print('UnrealCV server is not running. Run the game from http://unrealcv.github.io first.')
else:
print('Connected.')
filename = client.request('vget /camera/0/lit')

This simple demo can run successfully. As a result, a png figure of the game scene is saved to 'RealisticRendering/LinuxNoEditor/RealisticRendering/Binaries/Linux'. So, it seems that the environment in which I'm running the demo is correct.

However, I don't want to save the image to the hard disk. Instead, I'd like to transfer the image from the server to my algrithm directly. I read your Command List and noticed that the command

vget /camera/0/lit

which I used just now will store the image to the disk. But the command

vget /camera/0/lit png

can return the binary date through socket instead of saving it.
Moreover, I also noticed that in your faster_rcnn.py demo the above mentioned command is use in

res = client.request('vget /camera/0/lit png')

I just want to test this command, so I replaced the faster rcnn part with a function which takes in a image and return it immediately:

def faster_rcnn_detect(ax, frame):
return frame

Except for this modification, the complete code is mainly copied from the communication part of the faster_rcnn.py:

def faster_rcnn_detect(ax, frame):
return frame
def main(img_processor):
def capture_frame(func=None):
res = client.request('vget /camera/0/lit png')
im = read_png(res)
return im
def updatefig(*args):
frame = capture_frame(img_processor)
img_processor(ax, frame)
fig.canvas.draw()
return ax,
fig = plt.figure()
client.connect()
ani = animation.FuncAnimation(fig, updatefig, interval=50, blit=True)
fig, ax = plt.subplots()
plt.axis('off')
plt.tight_layout()
plt.show()
if name == 'main':
main(faster_rcnn_detect)

It is supposed to show the image of the current game scene when I clicked mouse in the game window.
However, the program crashed when I clicked in the game.
I printed the messages between server and client. Before clicking mouse, the client keeps sending messages like:

1:vget /camera/0/lit png
2:vget /camera/0/lit png
3:vget /camera/0/lit png

and receiving long messages seem like binary data.
But once clicked, the received message is:

clicked

It is strange because it does not match the [message_id:message_body] structure. This message can not be parsed so the demo crashed.
Why can't I receive correct message when clicked the mouse?