Request and Response

Messages exchanged by the client and the server are represented by a Request and a Response.

The client sends Requests to the server that include a service number, an optional subfunction and some data. The server processes the request and answers with a Response that contains an echo of the service number, a response code and some additional data.

The following classes provides the necessary interface to manipulate UDS requests and responses.

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Request

req = Request(service=ECUReset, subfunction=1, data=b'\x99\x88')
payload = req.get_payload()
print(payload) # b'\x11\x01\x99\x88'
req2 = Request.from_payload(payload)
print(req2) # <Request: [ECUReset] (subfunction=1) - 2 data bytes at 0x12345678>

class udsoncan.Request(service: typing.Union[udsoncan.BaseService.BaseService, typing.Type[udsoncan.BaseService.BaseService], NoneType] = None, subfunction: typing.Union[int, NoneType] = None, suppress_positive_response: bool = False, data: typing.Union[bytes, NoneType] = None)

Represents a UDS Request.

Parameters:

• service (class) – The service for which to make the request. This parameter must be a class that extends udsoncan.services.BaseService
• subfunction (int or None) – The service subfunction. This value may be ignored if the given service does not supports subfunctions
• suppress_positive_response (bool) – Indicates that the server should not send a response if the response code is positive. This parameter has effect only when the given service supports subfunctions
• data (bytes) – The service data appended after service ID and payload

Request.get_payload(suppress_positive_response: typing.Union[bool, NoneType] = None) → bytes

Generates a payload to be given to the underlying protocol. This method is meant to be used by a UDS client

Returns:A payload to be sent through the underlying protocol Return type:bytes

classmethod Request.from_payload(payload: bytes) → udsoncan.Request.Request

Creates a Request object from a payload coming from the underlying protocols. This method is meant to be used by a UDS server

Parameters:payload (bytes) – The payload of data to parse Returns:A Request object with populated fields Return type:Request

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Response

response = Response(service=ECUReset, code=Response.Code.PositiveResponse, data=b'\x11\x22')
payload = response.get_payload()
print(payload) # b'\x51\x11\x22'
response2 = Response.from_payload(payload)
print(response2) # <PositiveResponse: [ECUReset] - 2 data bytes at 0x7f9367e619b0>

class udsoncan.Response(service: typing.Union[udsoncan.BaseService.BaseService, typing.Type[udsoncan.BaseService.BaseService], NoneType] = None, code: typing.Union[int, NoneType] = None, data: typing.Union[bytes, NoneType] = None)

Represents a server Response to a client Request

Parameters:

• service (class) – The service implied by this response.
• code (int) – The response code
• data (bytes) – The response data encoded after the service and response code

valid

(boolean) True if the response content is valid. Only invalid_reason is guaranteed to have a meaningful value if this value is False

invalid_reason

(string) String explaining why the response is invalid.

service

(class) The response target service class

positive

(boolean) True if the response code is 0 (PositiveResponse), False otherwise

code

(int) The response code.

code_name

(string) The response code name.

data

(bytes) The response data. All the payload content, except the service number and the response code

service_data

(object) The content of data interpreted by a service; can be any type of content.

original_payload

(bytes) When the response is built with Response.from_payload, this property contains a copy of the payload used. None otherwise.

unexpected

(boolean) Indicates that the response was unexpected. Set by an external source such as the Client object

Response.get_payload() → bytes

Generates a payload to be given to the underlying protocol. This method is meant to be used by a UDS server

Returns:A payload to be sent through the underlying protocol Return type:bytes

classmethod Response.from_payload(payload: bytes) → udsoncan.Response.Response

Creates a Response object from a payload coming from the underlying protocol. This method is meant to be used by a UDS client

Parameters:payload (bytes) – The payload of data to parse Returns:A Response object with populated fields Return type:Response

Response Codes

Response.Code

alias of ResponseCode