How to create a distance matrix using the HC-SR04 sensor?

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47

This sends the value as text.

This reads the value as binary.

Text and binary are not the same thing. Try sending binary:

Serial.write((char *)&arrBuff[i], sizeof (float));

Does readPort() return the address of the buffer? If not you may need to fix the receiver code:

        arduino->readPort(incomingData, MAX_DATA_LENGTH);
	    float readResult = *(float *) incomingData;