Every HTTP upload method has two callbacks with signatures like this
onEmptyResponse: () => void, onServerReturnedSomething: ( errorCode: number, errorString: string, response: string) => void
The 1st callback
onEmptyResponse is triggered when the server returns no response string. Generally, if errors occurred on the server, the server would return some information to indicate what went wrong. Therefore, if nothing is returned, you can treat it as a successful upload.
Of course, in your own server-side script to accept and process the HTTP Post request, you know whether the upload is successful and can make it more obvious by returning some custom information to indicate that. In this case, the 2nd callback
onServerReturnedSomething will be triggered on purpose and you will need to read the argument
response which contains what is returned by the server.
When the callback
onServerReturnedSomethingis triggered, you will always get an
errorStringbut you can choose to ignore them if it’s triggered on purpose.
Dynamic Web TWAIN also provides an API called
HTTPPostResponseString which contains
response but can be read outside of the upload method.
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