Our automated invoice export workflow fails at the SFTP transfer step with ‘connection refused’ errors. The Integration Hub connector worked fine during initial testing but now fails in production with batch invoice processing.
Connection configuration:
Host: sftp.vendor.com
Port: 22
Auth: Service account key
Protocol: SFTP (SSH-2)
We’re using a dedicated service account for the connector, and our network team confirmed the firewall allows outbound port 22. Manual SFTP transfers from the same environment work using FileZilla. The issue only occurs when the RPA workflow triggers the batch export - individual invoice exports succeed. We suspect service account permissions, firewall configuration for automated high-volume transfers, or connector protocol settings might be causing the issue. Any insights would be appreciated.
Connection refused typically means the server is actively rejecting the connection, not that it’s unreachable. Check if your SFTP server has rate limiting or concurrent connection limits. Batch processing might be opening multiple simultaneous connections that exceed the server’s policy. Also verify that your firewall allows persistent connections, not just initial handshakes - some firewalls have aggressive timeout policies that drop idle SFTP connections during large file transfers.
Another angle: verify your firewall isn’t just allowing port 22 outbound, but also allowing the ephemeral port range for return traffic. SFTP uses port 22 for the control channel but opens random high ports (typically 1024-65535) for data transfer. Some corporate firewalls block these by default. Also check if your firewall has application-layer inspection for SSH that might be interfering with automated key-based auth versus password auth.
I manage SFTP servers and see this pattern often with service accounts. Most SFTP servers have stricter policies for automated accounts versus interactive users. Check your server’s sshd_config for MaxStartups and MaxSessions settings. Service accounts often hit these limits during batch operations. Also verify your service account isn’t locked due to failed authentication attempts - some systems auto-lock after 3-5 failures within a time window.