How to fix Error 4014 on Windows Server 2025 / Windows 11

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Why This Error Happens

Error 4014 typically occurs when the SQL Server network connection between the client and server is unexpectedly interrupted at the TCP/IP packet level. This is often caused by network instability, a misconfigured firewall dropping packets mid-session, antivirus/deep packet inspection software interfering with the TDS (Tabular Data Stream) protocol, or corrupted network drivers on Windows Server 2025 / Windows 11. It can also stem from client-side connection timeouts conflicting with long-running queries or large result sets being transmitted over an unstable link.

Step-by-Step Resolution Guide

Step 1: Verify Network Stability and Firewall Rules

  • Run ping <SQLServerInstanceName> and tracert <SQLServerInstanceName> continuously to check for packet loss or latency spikes.
  • Open Windows Defender Firewall with Advanced Security and confirm inbound/outbound rules allow TCP port 1433 (default instance) and any dynamic ports used by named instances.
  • Temporarily disable third-party antivirus/firewall software to rule out deep packet inspection interference, then re-test the connection.

Step 2: Check SQL Server Network Configuration

  • Open SQL Server Configuration Manager → SQL Server Network Configuration → Protocols for [InstanceName].
  • Ensure TCP/IP is enabled and verify the correct IP address/port bindings under the IP Addresses tab.
  • Restart the SQL Server (MSSQLSERVER) service after any configuration changes via services.msc or net stop MSSQLSERVER && net start MSSQLSERVER.

Step 3: Update Network Drivers and Adapter Settings

  • Navigate to Device Manager → Network Adapters, right-click the active NIC, and select Update Driver.
  • Disable TCP Chimney Offload and Receive Side Scaling (RSS) if packet corruption is suspected, using PowerShell: Disable-NetAdapterChecksumOffload -Name "*".
  • Reboot the server/workstation to apply the driver and adapter changes cleanly.

Step 4: Adjust Client and Server Timeout Settings

  • In your client application or SSMS, increase the Connection Timeout and Query Timeout values under Tools → Options → Query Execution.
  • On the server side, review sp_configure 'remote query timeout' and adjust if queries are being prematurely terminated.
  • Apply changes with RECONFIGURE and restart the SQL Server service to ensure settings take effect.

Alternative or Verification Steps

  • Reproduce the original workload (large query/data transfer) and monitor the SQL Server Error Log and Windows Event Viewer (Application log) to confirm Error 4014 no longer appears.
  • If the issue persists, capture a network trace using Wireshark or Netmon during the failure window to identify the exact point of packet loss, and share the trace with your network team for deeper TCP-level analysis.