Troubleshooting Outbound SFTP

Outbound SFTP connections can be interrupted by a variety of issues. Some are fixed by changing configuration settings in your Files.com site. Others must be addressed in the configuration of the remote SFTP system or its firewall.

Connection errors appear when you create or edit the Remote Server. Files.com records errors for individual file and folder operations in the Outbound Connections log. Some errors begin with a bracketed prefix that identifies the Remote Server by its ID and internal name.

Hostname Is Invalid

The error Hostname is invalid means Files.com cannot resolve the hostname of the remote SFTP server.

Enter the hostname without a protocol or path. Use a hostname that is resolvable from the public internet.

Incorrect Port for SFTP

The error Ports 21 and 990 are typically used for FTP, not SFTP means the specified port belongs to FTP(S) servers rather than SFTP servers. If the connection information you were given specifies ports 21 or 990, the remote server supports FTP(S) instead of SFTP. Add a remote server using the FTP protocol instead.

Connection Times Out

The error Timeout establishing ssh connection means Files.com cannot reach the remote SFTP server at the configured hostname and port.

Firewalls or other restrictions on the remote server can require an IP address to be allowlisted. Verify that connections from Files.com IP addresses are allowed by the remote SFTP server. Verify the IP addresses that are being used for connections from your Files.com site, and confirm that these IP addresses are not blocked by any firewalls.

When intermittent network issues exist between Files.com and the remote server, SFTP commands or their responses can fail to occur within the time allowed by the SFTP protocol.

When the remote SFTP server changes something, such as the authentication method or the SFTP port, SFTP connections from Files.com can time out because they are trying to connect using outdated information.

When the remote server is overloaded or runs out of resources, such as its CPU or memory hitting 100%, SFTP commands take much longer to execute. SFTP commands fail if the remote SFTP server does not respond within 45 seconds. We expect responses to take less than 5 to 10 seconds under normal conditions. A response time exceeding 45 seconds indicates a problem on the remote server.

SFTP servers can implement rate limits that cap the number of times the server can be connected to within a specified duration. Implementing dedicated IP addresses for your Files.com site helps mitigate rate limit issues.

Resolve any network issues and confirm that the remote SFTP server can support the connection load being sent to it from Files.com. Confirm that combined workloads from all Syncs, Remote Mounts, and Automations to the remote server stay within its operational limits.

Authentication Failed

The error Authentication failed - Verify credentials (password) and also confirm that Files.com IPs are whitelisted. means the remote SFTP server rejected the credentials that Files.com presented. The text in parentheses names the authentication method configured for the connection. A connection that authenticates with a private key shows (private key).

Check that the username, password or private key, and authentication method match what the remote SFTP server requires. Some SFTP servers also reject connections from IP addresses that have not been allowlisted. Confirm that the remote SFTP server allows connections from Files.com IP addresses.

Server Refused the Connection

The error Connection failed: The server refused the connection during authentication means the remote server ended the connection before authentication completed.

This occurs when the service at the configured hostname and port is not an SFTP server. For example, connecting to an FTP(S) service on port 990 produces this error.

This also occurs when the remote SFTP server and Files.com cannot agree on the SSH algorithms used for the connection. Connections to a remote SFTP server use the algorithm cipher agreed upon by both Files.com and the remote system. Files.com presents a list of algorithm ciphers, starting with the strongest and ending with the weakest, to the remote SFTP server. The remote server decides which algorithms are used for Key Exchange, Server Host Key, Encryption, and MAC. Contact the administrator of the remote SFTP server to determine which SSH algorithm ciphers that system supports.

Some SFTP servers allow customization or are implemented in a non-standard way. Connectivity to non-standard SFTP servers is not always successful.

Host Key Mismatch

The error Host key mismatch means the host key presented by the remote SFTP server does not match the Server Host Key configured for the Remote Server. This occurs when the remote server's host key has changed.

Obtain the current host key from the administrator of the remote SFTP server and update the Server Host Key setting for the Remote Server.

Permissions Error

The error Permissions Error means the user account that Files.com uses to connect does not have permission to perform the attempted operation on the remote SFTP server.

Files.com records the failed operation in the Outbound Connections log along with the operation type and error message. Ask the administrator of the remote SFTP server to grant the account the permissions the operation needs.