TCP/IP connection problems

I try to use Pyvisa and Pyvisa-py to control several instruments through Ethernet. Everything works well except an Anritsu Signal Generator named MG3694C. I got the error :

[Command: python3 -u /home/quantum/Downloads/MG3694C.py]
Traceback (most recent call last):
  File "/home/quantum/Downloads/MG3694C.py", line 11, in <module>
    print(inst.query('*IDN?'))
  File "/usr/local/lib/python3.6/dist-packages/pyvisa/resources/messagebased.py", line 558, in query
    self.write(message)
  File "/usr/local/lib/python3.6/dist-packages/pyvisa/resources/messagebased.py", line 223, in write
    count = self.write_raw(message.encode(enco))
  File "/usr/local/lib/python3.6/dist-packages/pyvisa/resources/messagebased.py", line 201, in write_raw
    return self.visalib.write(self.session, message)
  File "/usr/local/lib/python3.6/dist-packages/pyvisa-py/highlevel.py", line 373, in write
    raise errors.VisaIOError(ret[1])
pyvisa.errors.VisaIOError: VI_ERROR_IO (-1073807298): Could not perform operation because of I/O error.

My code is simple, and the same code (different address) works well to all other instruments :

import visa
import numpy as np
rm = visa.ResourceManager('@py')
ipaddr = 'TCPIP0::192.168.0.254::INSTR'
inst = rm.get_instrument(ipaddr)
print(inst.query('*IDN?'))

I spent a lot of time searching online try to find a solution, but failed. The problem seems to be in the buffer size, like in https://github.com/pyvisa/pyvisa/issues/174. However, the definition of the set_buffer function in pyvisa-py seems has not been finished. As follow:

#/usr/local/lib/python3.6/dist-packages/pyvisa/highlevel.py
def set_buffer(self, session, mask, size):
    """Sets the size for the formatted I/O and/or low-level I/O communication buffer(s).

    Corresponds to viSetBuf function of the VISA library.

    :param session: Unique logical identifier to a session.
    :param mask: Specifies the type of buffer. (Constants.VI_READ_BUF, .VI_WRITE_BUF, .VI_IO_IN_BUF, .VI_IO_OUT_BUF)
    :param size: The size to be set for the specified buffer(s).
    :return: return value of the library call.
    :rtype: :class:`pyvisa.constants.StatusCode`
    """
    raise NotImplementedError

More details of my computer:

Machine Details:
   Platform ID:    Linux-4.15.0-39-generic-x86_64-with-Ubuntu-18.04-bionic
   Processor:      x86_64

Python:
   Implementation: CPython
   Executable:     /usr/bin/python3
   Version:        3.6.7
   Compiler:       GCC 8.2.0
   Bits:           64bit
   Build:          Oct 22 2018 11:32:17 (#default)
   Unicode:        UCS4

PyVISA Version: 1.10.0.dev0

Backends:
   ni:
      Version: 1.10.0.dev0 (bundled with PyVISA)
      Binary library: Not found
   py:
      Version: 0.3.1
      ASRL INSTR: Available via PySerial (3.4)
      USB INSTR: Available via PyUSB (1.0.2). Backend: libusb1
      USB RAW: Available via PyUSB (1.0.2). Backend: libusb1
      TCPIP INSTR: Available 
      TCPIP SOCKET: Available 
      GPIB INSTR:
         Please install linux-gpib to use this resource type.
         No module named 'gpib'

I’m new to visa. So how can I fix this issue? Can anyone help?

[MatthieuDartiailh]

Can you try the following ? This will be closer to the vxi11 example since INSTR resources on TCPIP uses the vxi11 protocol by default.

>>> import pyvisa
>>> rm = pyvisa.ResourceManager()
>>> dmm = rm.open_resource("TCPIP::192.168.1.221::INSTR")
>>> dmm.query('*IDN?')

[MatthieuDartiailh]

Happy to help !