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raw socket communication example
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‎Python/Thorlabs PMxxx Power Meters/SCPI/ethernetRawSockets/Readme.md‎

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# Ethernet Raw Socket Communication
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This python command line sample demonstrates how to communicate with a Thorlabs Ethernet capable power meter using
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raw python socket communication without any additional library like anyvisa.
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# Details
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The powermeter uses a binary protocol to frame large request/response messages to multiple TCP packets. The given codes
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uses synchronous IO to implement this binary protocol for data exchange. The example does not contain any network device
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discovery. You need to know the IP and port number of the power meter to connect. Once the connection is established you
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can use the methods to send and receive text and binary request and response data. The implementation is totally platform
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independent.
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For more technical background information about fast mode refer to SCPI command description. You can find a description for
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every Meter in the [commandDocu](../commandDocu) folder. For example the PM103E [SCPI command description](https://htmlpreview.github.io/?https://github.com/Selanarixx/Light_Analysis_Examples/blob/develop/Python/Thorlabs%20PMxxx%20Power%20Meters/scpi/commandDocu/pm103E.html) html file.
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## Limitations
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Please be aware the power meter will close the connection automatically if no communication is ongoing for 30 seconds.
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If you send an ernous (e.g. an unkown SCPI command) request, the receive function will issue a timeout error as the
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device does not send any response data.
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## Supported Meters
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- PM103E
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- PM5020

‎Python/Thorlabs PMxxx Power Meters/SCPI/ethernetRawSockets/pmNetFormat.py‎

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"""
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Example Thorlabs Power Meter raw ethernet socket communication
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Example Date of Creation 2024-08-07
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Example Date of Last Modification on Github 2024-08-07
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Version of Python 3.11.2
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Version of the Thorlabs SDK used none
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==================
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This examples shows how to communicate with a Thorlabs ethernet capable
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Power Meter using raw python socket communication. The sample implements
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the binary framing protocol to transfer SCPI request and response data
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as payload.
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"""
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import struct
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import socket
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#Maximal size of a TCP segment of the Thorlabs power meter
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TCP_MAX_SEG_SIZE = 1440
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#Size of the header in bytes of a TCP segment of the Thorlabs power meter
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TL_TCP_SEG_HEADER_SIZE = 4
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#Maximal amount of payload bytes for a single frame
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MAX_FRAME_LEN = TCP_MAX_SEG_SIZE - TL_TCP_SEG_HEADER_SIZE
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def TL_TCP_frame_transmit_bin(socket: socket, request: bytearray):
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"""
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Transmits a binary request to the Thorlabs power meter.
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The request is split into multiple frames if it is too large.
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:param socket: The openend socket to use for transmission
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:param request: The binary request to transmit to power meter
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"""
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reqLen = len(request)
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writtenBytes = 0
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frameCnt = 0
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while writtenBytes < reqLen:
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#Limit max lenth of request
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frameLen = reqLen - writtenBytes
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if frameLen > MAX_FRAME_LEN:
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frameLen = MAX_FRAME_LEN
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binReq = []
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if frameCnt == 0:
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binReq = struct.pack('<cch', bytes([0xCA]), bytes([frameCnt]), reqLen)
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binReq = binReq + request[writtenBytes : frameLen]
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else:
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binReq = struct.pack('<cch', bytes([0xCB]), bytes([frameCnt]), frameLen)
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binReq = binReq + request[writtenBytes : writtenBytes+frameLen]
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#Send segment to server
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socket.sendall(binReq)
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frameCnt += 1
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writtenBytes += frameLen
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def TL_TCP_frame_receive_bin(socket: socket):
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"""
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Receives a binary response from the Thorlabs power meter.
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The response is assembled from multiple frames.
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You might want to set the timeout of the socket
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to avoid endless blocking. See socket.settimeout().
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If there has been an enour request send before, the
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function will also return a timeout error.
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:param socket: The openend socket to use for reception
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:return: The binary response from power meter
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"""
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resp = bytearray()
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respIdx = 0
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respHeader = bytearray(TL_TCP_SEG_HEADER_SIZE)
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respHeaderLen = 0
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respHeadSeq = 0
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respBinSegLen = 0
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respBinTotalLen = 0
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while True:
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data = socket.recv(1500)
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#Iterate all received bytes
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for d in data:
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#Already parsed frame start header?
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if respBinTotalLen == 0:
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#Waiting for start of frame header
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if d != 0xCA and respHeaderLen == 0:
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continue
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respHeader[respHeaderLen] = d
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respHeaderLen += 1
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#Parsed entire header?
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if respHeaderLen == TL_TCP_SEG_HEADER_SIZE:
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#Verify header?
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if respHeader[1] != 0:
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respBinSegLen = respBinTotalLen = 0
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else:
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respBinSegLen = respBinTotalLen = struct.unpack('<h', respHeader[2:4])[0]
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if respBinSegLen > MAX_FRAME_LEN:
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respBinSegLen = MAX_FRAME_LEN
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respHeadSeq = 1
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resp = bytearray(respBinTotalLen)
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respIdx = 0
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#Finally reset header parsing memory
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respHeaderLen = 0
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else:
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#Wait for start of conintous header?
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if respBinSegLen == 0:
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#Wait for start of continous frame
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if d != 0xCB and respHeaderLen == 0:
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continue
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respHeader[respHeaderLen] = d
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respHeaderLen += 1
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#Parsed entire header?
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if respHeaderLen == TL_TCP_SEG_HEADER_SIZE:
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#Verify header sequence number
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if respHeader[1] != respHeadSeq:
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respBinSegLen = respBinTotalLen = 0
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else:
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respBinSegLen = struct.unpack('<h', respHeader[2:4])[0]
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respHeadSeq += 1
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#Ensure segment size is not larger than expected total payload
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if respBinSegLen > respBinTotalLen:
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respBinSegLen = respBinTotalLen = 0
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#Empty header? We are done -> go back to init
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if respBinSegLen == 0:
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respBinSegLen = respBinTotalLen = 0
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#Finally reset header parsing memory
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respHeaderLen = 0
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else:
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#Append data to response
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resp[respIdx] = d
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respIdx += 1
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respBinSegLen -= 1
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respBinTotalLen -= 1
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if respBinTotalLen == 0:
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return resp
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def TL_TCP_frame_receive(socket: socket):
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"""
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Receives a text response from the Thorlabs power meter.
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The response is assembled from multiple frames.
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For closer details read TL_TCP_frame_receive_bin()
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comments.
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:param socket: The openend socket to use for reception
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"""
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binResp = TL_TCP_frame_receive_bin(socket)
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return binResp.decode('ASCII')
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def TL_TCP_frame_transmit(socket: socket, req:str):
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"""
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Transmits a text request to the Thorlabs power meter..
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The request is split into multiple frames if it is too large.
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:param socket: The openend socket to use for transmission
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:param req: The text request to transmit to power meter
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"""
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return TL_TCP_frame_transmit_bin(socket, req.encode('ASCII'))
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def TL_TCP_query(socket: socket, req:str):
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"""
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Sends a text request to the Thorlabs power meter and returns the text response.
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:param socket: The openend socket to use for transmission
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:param req: The text request to transmit to power meter
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"""
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TL_TCP_frame_transmit(socket, req)
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return TL_TCP_frame_receive(socket).strip()
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def TL_TCP_query_bin(socket: socket, req:str):
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"""
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Sends a text request to the Thorlabs power meter and returns the binary response.
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:param socket: The openend socket to use for transmission
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:param req: The text request to transmit to power meter
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"""
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TL_TCP_frame_transmit(socket, req)
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return TL_TCP_frame_receive_bin(socket)
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if __name__ == '__main__':
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with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
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#Set connection timeout
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s.settimeout(2)
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#Connect to PM with given IP and port number. Default port is 2000.
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s.connect(("10.10.4.22", 2000))
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#Set read timeout
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s.settimeout(1)
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print(TL_TCP_query(s,"*IDN?\n"))
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print(TL_TCP_query(s,"SYST:ERR?\n"))

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