Why Does Curl Return \'Transfer Closed with Outstanding Read Data Remaining\' (Error 18) and How Can I Fix It?

Error 18: Understanding "Transfer Closed with Outstanding Read Data Remaining" in Curl

When utilizing curl to retrieve data from a URL, you may encounter Error 18: "transfer closed with outstanding read data remaining." This puzzling error results in missing data from your response.

Contributing Factor: Chunked Encoding

This error typically occurs when retrieving data via chunked encoding. Curl expects to receive chunks of data from the server. In this case, the connection is prematurely closed before all chunks are received, resulting in an incomplete dataset.

Potential Causes

This issue can stem from server-side issues, network connectivity problems, or a combination of both. The server may be sending chunked data but failing to complete the transfer due to server malfunction or network instability.

Avoiding the Error

Although you cannot directly mitigate this error by modifying your request, you can try the following workaround:

• Send an HTTP 1.0 request instead of an HTTP 1.1 request. Chunked encoding is not used in HTTP 1.0, which may resolve the issue.

Caveats

Note that this workaround may be temporary, and the underlying issue likely lies with the server or network setup. Consult with the server's administrator or your network provider to resolve the root cause.

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