Network Transport Errors

Estimated reading time: 7 minutes


The network transport layer is responsible for the reliable transmission of data between devices over a network. The transport layer is typically implemented in protocols such as TCP (Transmission Control Protocol) or UDP (User Datagram Protocol). Sometimes in the course of operations, transport errors can occur during the transmission of data between a client and a server.

Network connectivity problems have various causes, but they typically occur because of incorrect network adapters, incorrect switch settings, faulty hardware, or driver issues. Some connectivity symptoms are intermittent and do not clearly point to any one of these causes.

Types of Transport Errors

Connection Refused: This error occurs when attempting to establish a connection to a server that actively refuses the connection. It could indicate that the server is not running or is configured to reject connections from certain clients.

Connection Reset by Peer: This error occurs when the remote server abruptly terminates an established connection. It could happen due to various reasons such as the server crashing, network issues, or misconfiguration.

Network Unreachable: This error indicates that the network path to the destination is unreachable. It could occur due to routing issues, network configuration problems, or hardware failures.

Port Unreachable: This error occurs when trying to establish a connection to a specific port on a server that is not listening on that port or is blocked by a firewall.

No Route to Host: This error indicates that there is no valid route to reach the destination host. It could occur due to misconfigured routing tables or network congestion.

Packet Too Large: This error occurs when trying to transmit a packet that exceeds the maximum transmission unit (MTU) size of the network. It could happen if the packet size is too large or if there are issues with the network path's MTU settings.

Timeout Error: This error occurs when a connection or operation takes longer than the specified timeout period. It could indicate network congestion, server overload, or issues with the remote server's responsiveness. The semaphore timeout period has expired" is a network related error, not a SQL Server timeout. The source of the issue can be related to your VPN if you are using a VPN or to Network connectivity problems


When troubleshooting TCP Provider errors, it's essential to consider factors such as network connectivity, firewall settings, SQL Server configuration, and server availability. Here are some suggestions:

Check Network Connectivity: Verify that there are no issues with the network connectivity between the client and server. You can do this by pinging the server, checking for any network outages, or using network diagnostic tools.

Verify Server Availability: Ensure that the server is running and accessible. Check if other clients can connect to the server successfully. If the server is down or inaccessible, investigate the cause, such as server hardware failures, software crashes, or misconfigurations.

Review Server Logs: Examine the server logs for any errors or warnings related to network communication. Server logs can provide valuable insights into the underlying issues causing transport errors.

Check Firewall Settings: Verify that the firewall settings on both the client and server allow traffic on the necessary ports and protocols. Ensure that there are no rules blocking communication between the client and server.

Inspect Network Configuration: Review the network configuration settings on both the client and server. Check IP addresses, subnet masks, gateways, DNS settings, and other network parameters to ensure they are configured correctly.

Test with Different Clients/Devices: If possible, test communication with the server using different clients or devices. This can help determine if the issue is specific to a particular client or if it affects multiple devices.

Update Network Drivers/Firmware: Ensure that the network drivers and firmware on both the client and server are up to date. Outdated drivers or firmware can cause compatibility issues and impact network performance.

Adjust Timeout Settings: If the error message indicates a timeout issue, consider adjusting timeout settings on both the client and server to allow for longer wait times before triggering a timeout.

Monitor Network Traffic: Use network monitoring tools to analyze network traffic between the client and server. Look for any abnormalities, packet loss, or excessive latency that could indicate underlying network issues.

Consult Documentation or Support: If you're unable to resolve the issue on your own, consult documentation related to the software or hardware involved. You can also reach out to vendor support for assistance in troubleshooting and resolving transport-level errors.