(UE5 / Humble) De-/serialization problem when trying to publish sensor_msgs/Image or CompressedImage

[agaertner]

stacktrace:

[rosbridge_tcp-1] [INFO] [1673531368.773922849] [rosbridge_tcp]: [Client 0] Subscribed to /unreal/observer_image
[rosbridge_tcp-1] [ERROR] [1673531373.971018822] [rosbridge_tcp]: [Client 0] [id: publish:/unreal/observer_image:288] publish: Message type sensor_msgs/Image does not have a field header.seq
[rosbridge_tcp-1] [ERROR] [1673531373.980958077] [rosbridge_tcp]: [Client 0] [id: publish:/unreal/observer_image:290] publish: Message type sensor_msgs/Image does not have a field header.seq
[rosbridge_tcp-1] [ERROR] [1673531374.040446020] [rosbridge_tcp]: [Client 0] Exception in deserialization of BSON
[rosbridge_tcp-1] exc in handle/recv_bson: (<class 'SyntaxError'>, SyntaxError('invalid syntax', ('<string>', 0, 0, '', 0, 0)), <traceback object at 0x7f9a6b1cc680>)
[rosbridge_tcp-1] Traceback (most recent call last):
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 109, in handle
[rosbridge_tcp-1]     if self.recv_bson() is None:
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 85, in recv_bson
[rosbridge_tcp-1]     data = self.recvall(msglen - BSON_LENGTH_IN_BYTES)
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 74, in recvall
[rosbridge_tcp-1]     return eval(bytes(data,'utf-8'))
[rosbridge_tcp-1]   File "<string>", line 0
[rosbridge_tcp-1]     
[rosbridge_tcp-1] SyntaxError: invalid syntax
[rosbridge_tcp-1] exc in handle/recv_bson: (<class 'SyntaxError'>, SyntaxError('invalid syntax', ('<string>', 0, 0, '', 0, 0)), <traceback object at 0x7f9a6b1afb00>)
[rosbridge_tcp-1] exc in handle/recv_bson: (<class 'SyntaxError'>, SyntaxError('invalid syntax', ('<string>', 0, 0, '', 0, 0)), <traceback object at 0x7f9a6b1afb00>)
[rosbridge_tcp-1] Traceback (most recent call last):
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 109, in handle
[rosbridge_tcp-1]     if self.recv_bson() is None:
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 85, in recv_bson
[rosbridge_tcp-1]     data = self.recvall(msglen - BSON_LENGTH_IN_BYTES)
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 74, in recvall
[rosbridge_tcp-1]     return eval(bytes(data,'utf-8'))
[rosbridge_tcp-1]   File "<string>", line 0
[rosbridge_tcp-1]     
[rosbridge_tcp-1] SyntaxError: invalid syntax
[rosbridge_tcp-1] Traceback (most recent call last):
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 109, in handle
[rosbridge_tcp-1]     if self.recv_bson() is None:
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 85, in recv_bson
[rosbridge_tcp-1]     data = self.recvall(msglen - BSON_LENGTH_IN_BYTES)
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 74, in recvall
[rosbridge_tcp-1]     return eval(bytes(data,'utf-8'))
[rosbridge_tcp-1]   File "<string>", line 0
[rosbridge_tcp-1]     
[rosbridge_tcp-1] SyntaxError: invalid syntax
[rosbridge_tcp-1] Traceback (most recent call last):
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 109, in handle
[rosbridge_tcp-1]     if self.recv_bson() is None:
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 85, in recv_bson
[rosbridge_tcp-1]     data = self.recvall(msglen - BSON_LENGTH_IN_BYTES)
[rosbridge_tcp-1]   File "/home/agaertner/ros2_humble/ros2_ws/install/rosbridge_server/local/lib/python3.10/dist-packages/rosbridge_server/tcp_handler.py", line 74, in recvall
[rosbridge_tcp-1]     return eval(bytes(data,'utf-8'))
[rosbridge_tcp-1]   File "<string>", line 0
[rosbridge_tcp-1]     
[rosbridge_tcp-1] SyntaxError: invalid syntax
[rosbridge_tcp-1] exc in handle/recv_bson: (<class 'SyntaxError'>, SyntaxError('invalid syntax', ('<string>', 0, 0, '', 0, 0)), <traceback object at 0x7f9a6b1afb00>)

I am using naxsm fork of rosbridge_suite and have tried the fork of tsender both error with a missing header.seq field.

My message creation functions for Compressed or NonCompressed images are as follows:

bool UTopic::PublishCompressedImageMessage(const TArray<uint8>& imageData, const ECompressedImageFormat& format, const FString& frameId) {
	
	FString fmt;
	switch (format) 
	{
		case ECompressedImageFormat::Jpeg: 
		{
			fmt = "jpeg"; 
			break;
		} 
		case ECompressedImageFormat::Png: 
		{
			fmt = "png"; 
			break;
		}
		default: return false;
	}

	if (!_State.Advertised)
	{
		if (!Advertise())
		{
			return false;
		}
	}

	TSharedPtr<ROSMessages::sensor_msgs::CompressedImage> msg = MakeShareable(new ROSMessages::sensor_msgs::CompressedImage);

	TSharedPtr<ROSMessages::std_msgs::Header> header = MakeShareable(new ROSMessages::std_msgs::Header(1, FROSTime::Now(), frameId, true));
	msg->header = *header;
	msg->data_size = imageData.Num();
	msg->data = imageData.GetData();
	msg->format = fmt;
	return _Implementation->Publish(msg);
}

bool UTopic::PublishImageMessage(const int32& height, const int32& width, const FString& encoding, const bool& isBigEndian, const int32& rowLength, const TArray<uint8>& imageData, const FString& frameId) {
	if (!_State.Advertised)
	{
		if (!Advertise())
		{
			return false;
		}
	}

	TSharedPtr<ROSMessages::sensor_msgs::Image> msg = MakeShareable(new ROSMessages::sensor_msgs::Image);

	TSharedPtr<ROSMessages::std_msgs::Header> header = MakeShareable(new ROSMessages::std_msgs::Header(1, FROSTime::Now(), frameId, true));
	msg->header = *header;
	msg->height = height;
	msg->width = width;
	msg->encoding = encoding;
	msg->is_bigendian = isBigEndian;

	msg->step = imageData.Num();
	msg->data = imageData.GetData();

	return _Implementation->Publish(msg);
}
``