Curl error 55 means “Failed sending network data”, which happens during file uploads.

Here at Bobcares, we have seen several curl errors as part of our Server Management Services for web hosts and online service providers.

Today we’ll take a look at the cause for this error and see how to fix it.

What is curl 55

Customers can encounter curl errors at different times due to various reasons such as improper installation,  outdated versions, etc. Similarly, a curl error occurs when uploading files to the server. More accurately, the error is a representation of Failed sending data via a network.

Here is the complete error message:

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curl: (55) SSL read: error:00000000:lib(0):func(0):reason(0), errno 10054

~~~

Causes and how we fixed the Curl error 55

Now let’s see the reasons for the curl error and how our Support Engineers resolve this error to our customers.

1.  Insufficient quotas: One of the reasons for the error in the FTP server is due to Insufficient quotas like hard disk quota, which is provided for the user.

For example, sometimes the Backup to the remote FTP server fails with the error:

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Error: server “server”
Curl error: Unable to resume an interrupted upload: (55) Failed sending data to the peer: Last FTP request: APPE backup_1801300838.zip: Last FTP response: 150 Opening BINARY mode data connection for backup_1801300838.zip: Connection to the FTP server has lost

~~~

That is, this error occurs when the FTP server or FTP user exceeded quotas or limits in the middle of the process.

Therefore, our Support Engineers check and adjust the limits and quotas for the FTP server and user.

2. Firewall not properly configured: Firewall is a network security system that helps to controls the traffic to a server based on a predetermined set of rules.

So, the bad settings in the firewall configuration result in the curl error. So, it is necessary to configure the firewall properly.

Therefore, our Support Engineers make sure that the necessary inbound and outbound connections are allowed in the firewall.

3. Outdated version: The multiple appearances of Content-Length headers can also cause the curl error.

Then, upgrade the version of curl to the latest can fix the error.

4. Incorrect time settings: Sometimes, the error happens when the time of the client or server is different than the real-time

So, our Support Engineers checks and corrects the time settings on the server.

5. Missing flags: Also, if the –header flag not used for each header, the Curl error 55

Then, our Support Engineers use a separate –header flag for each header that wishes to set.

[Need any further assistance in fixing curl errors? – We’re available 24*7]

Conclusion

In short, the Curl error 55 happens when fails to upload the file to the server. the reasons include Insufficient quotas, improper firewall settings, incorrect time settings, etc. Today, we saw how our Support Engineers fix this curl error.