How to fix Error 4002 on Windows Server 2025 / Windows 11

by

Troubleshooting Guide: SQL Server Error 4002 – Incorrect TDS Protocol Stream

Why This Error Happens

This error typically occurs when the Tabular Data Stream (TDS) packets sent between the client and SQL Server 2025 are malformed, truncated, or interrupted mid-transmission. Common root causes include network instability or packet fragmentation, a mismatch between the client driver version and the server’s TDS protocol version, or interference from a firewall/antivirus application inspecting and altering the traffic. It can also result from an unstable or improperly closed connection pool on the application side.

Step-by-Step Resolution Guide

Step 1: Verify Network Stability and Packet Integrity

  • Run ping -t <ServerName> for an extended period to check for packet loss or latency spikes.
  • Check for network card driver issues in Windows 11/Server 2025 via Device Manager.
  • Disable TCP Chimney Offload and Receive Side Scaling (RSS) temporarily using netsh int tcp set global rss=disabled to rule out NIC offloading bugs.

Step 2: Update Client Drivers and Connection Strings

  • Ensure the client is using the latest Microsoft ODBC Driver or OLE DB Driver compatible with SQL Server 2025.
  • Check the application’s connection string for Encrypt and TrustServerCertificate settings, as TLS handshake failures can sometimes manifest as TDS stream errors.
  • Update the driver via the official Microsoft Download Center rather than relying on cached OS drivers.

Step 3: Adjust SQL Server Network Configuration

  • Open SQL Server Configuration Manager.
  • Navigate to SQL Server Network Configuration > Protocols for MSSQLSERVER.
  • Ensure “TCP/IP” is enabled and check the IPAll section to verify the correct Port (default 1433) is set without conflicting duplicate entries.
  • Restart the MSSQLSERVER service to apply changes.

Step 4: Check Firewall and Antivirus Packet Inspection

  • Temporarily disable Windows Defender Firewall or third-party antivirus software to see if the error persists.
  • If disabling resolves the issue, create a specific inbound/outbound rule for port 1433 to exclude SQL traffic from deep packet inspection.
  • Verify no Intrusion Detection System (IDS) is truncating large TDS packets sent during bulk data transfers.

Alternative or Verification Steps

  • Run a test query via SQL Server Management Studio (SSMS) immediately after applying the fixes to ensure the connection remains stable for at least 10 minutes without dropping.
  • If the error persists only during large data transfers, set the Network Packet Size property in the connection string to a lower value (e.g., 4096) to prevent oversized TDS packets from being rejected by intermediary network hardware.