DownloadFileChunk

# DownloadFileChunk API

Downloads a single chunk of a staged file using an open download handler. Returns the chunk bytes as base64-encoded content inside an XML element, along with metadata about the chunk and the total file. This is the second step in the chunked download workflow.

Endpoint¶

/srv.asmx/DownloadFileChunk

Methods¶

GET /srv.asmx/DownloadFileChunk?authenticationTicket=...&DownloadHandler=...&StartOffset=...&ChunkSize=...
POST /srv.asmx/DownloadFileChunk (form data)
SOAP Action: http://tempuri.org/DownloadFileChunk

Parameters¶

Parameter	Type	Required	Description
`authenticationTicket`	string	Yes	Authentication ticket obtained from `AuthenticateUser`.
`DownloadHandler`	string (GUID)	Yes	The handler GUID returned by `GetDownloadHandler`, `GetDownloadHandlerByVersion`, or `DownloadZipWithHandler`. Must be a valid GUID string.
`StartOffset`	int	Yes	Byte offset within the file at which to begin reading. Use `0` for the first chunk. For each subsequent chunk, increment by the previous chunk's `chunklength` value.
`ChunkSize`	int	Yes	Maximum number of bytes to read for this chunk. The actual bytes returned may be less for the final chunk.

Response¶

Success Response¶

The chunk bytes are returned as base64-encoded text in the XML element body. File metadata and chunk integrity information are provided as attributes.

<response success="true"
          filelength="1048576"
          chunklength="65536"
          lastchunk="false"
          chunkCRC32="a3f1c29d">
  JVBERi0xLjQKJeLjz9MKNiAwIG9iag==...
</response>

Attribute	Type	Description
`success`	bool	`true` if the chunk was read successfully.
`filelength`	int	Total size of the staged file in bytes. Use this to calculate the total number of chunks.
`chunklength`	int	Actual number of bytes returned in this chunk. May be less than `ChunkSize` for the final chunk. Always use `chunklength` (not `ChunkSize`) when advancing `StartOffset`.
`lastchunk`	bool	`"true"` when this is the last chunk of the file (`StartOffset + ChunkSize >= filelength`). Stop iterating when this is `"true"`.
`chunkCRC32`	string	CRC32 checksum of this chunk's bytes. Use to verify chunk integrity after decoding from base64.
(body)	string	Base64-encoded bytes of the chunk content.

Error Response¶

<response success="false" error="Error message" />

Required Permissions¶

Any authenticated user may call this API. The download handler must have been created by the same authenticated user's session.

Chunked Download Workflow¶

GetDownloadHandler (or GetDownloadHandlerByVersion / DownloadZipWithHandler) — Prepare the file and obtain a DownloadHandler GUID and the total file size.
DownloadFileChunk (this API) — Call repeatedly, advancing StartOffset by chunklength after each response, until lastchunk="true".
DeleteDownloadHandler — Clean up the handler and its temporary file.

Iteration Example¶

// First chunk
StartOffset=0, ChunkSize=65536
→ chunklength=65536, lastchunk="false"

// Second chunk
StartOffset=65536, ChunkSize=65536
→ chunklength=65536, lastchunk="false"

// Final chunk (file size = 180000 bytes)
StartOffset=131072, ChunkSize=65536
→ chunklength=48928, lastchunk="true"  ← stop here

Always advance StartOffset by chunklength (not ChunkSize) to correctly handle the shorter final chunk.

Example¶

GET Request¶

GET /srv.asmx/DownloadFileChunk
  ?authenticationTicket=3f2504e0-4f89-11d3-9a0c-0305e82c3301
  &DownloadHandler=a1b2c3d4-e5f6-7890-abcd-ef1234567890
  &StartOffset=0
  &ChunkSize=65536
HTTP/1.1

POST Request¶

POST /srv.asmx/DownloadFileChunk HTTP/1.1
Content-Type: application/x-www-form-urlencoded

authenticationTicket=3f2504e0-4f89-11d3-9a0c-0305e82c3301
&DownloadHandler=a1b2c3d4-e5f6-7890-abcd-ef1234567890
&StartOffset=0
&ChunkSize=65536

SOAP Request¶

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
               xmlns:tns="http://tempuri.org/">
  <soap:Body>
    <tns:DownloadFileChunk>
      <tns:authenticationTicket>3f2504e0-4f89-11d3-9a0c-0305e82c3301</tns:authenticationTicket>
      <tns:DownloadHandler>a1b2c3d4-e5f6-7890-abcd-ef1234567890</tns:DownloadHandler>
      <tns:StartOffset>0</tns:StartOffset>
      <tns:ChunkSize>65536</tns:ChunkSize>
    </tns:DownloadFileChunk>
  </soap:Body>
</soap:Envelope>

Notes¶

The chunk content is base64-encoded in the XML body — decode it before writing to the output file.
Use chunklength (not ChunkSize) when advancing StartOffset to correctly handle the shorter final chunk.
Check chunkCRC32 after decoding each chunk to verify it was not corrupted in transit.
Stop iterating when lastchunk="true". Do not make a further call with the next offset.
Passing a string that is not a valid GUID for DownloadHandler returns an error immediately.
If the handler file has been deleted or expired, an error is returned.
After all chunks are collected, call DeleteDownloadHandler to free the temporary file on the server.

GetDownloadHandler - Prepare a document for chunked download and obtain the handler GUID
GetDownloadHandlerByVersion - Prepare a specific document version for chunked download
DownloadZipWithHandler - Prepare a zip archive of folders and documents for chunked download
DeleteDownloadHandler - Clean up the download handler after all chunks are retrieved
UploadFileChunk - Upload counterpart for chunked uploads

Error Codes¶

Error	Description
`[900] Authentication failed`	Invalid or missing authentication ticket.
`[901] Session expired or Invalid ticket`	The ticket has expired or does not exist.
`Invalid download handler. (guid)`	`DownloadHandler` is not a valid GUID string.
Handler not found	The handler file does not exist (deleted or expired).

For detailed documentation visit: https://support.inforouter.com/api-docs/DownloadFileChunk