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.

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=None, subfunction=None, suppress_positive_response=False, data=None)[source]

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=None)[source]

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
Parameters:: suppress_positive_response (bool | None) –

classmethod Request.from_payload(payload)[source]

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

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=None, code=None, data=None)[source]

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

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

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.

original_request: (Request) Optional reference to the request object that generated this response.

Response.get_payload()[source]

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)[source]

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