Windows Sockets are an application program interface (API) that allow communication between two systems over a network. Socket errors can be caused by various issues including connectivity problems on the network, client or server computers or due to a firewall, antivirus or a proxy server.

This article provides information about common socket errors you may encounter when using FTP, Cloud, SBMS or Email with SyncBack:

Socket error # 10013, Permission denied

This error occurs when the socket connection to the remote server is denied. The possible reasons are a firewall or antivirus (AV) software is blocking the connection, the port used is blocked or unreachable.

Temporarily disable firewall/AV program and check the connection after restarting your computer.

Socket Error # 10039, Destination address required

There may be a problem getting the IP address for the hostname.

Socket error # 10052, Network dropped connection on reset

The host you are connecting to crashed or rebooted. Retry later.

Socket error # 10053, Software caused connection abort

An established connection was closed by software on your local host. Possibly a firewall, AV or something else on your local computer aborted the connection, or the connection to the remote server timed out.

Socket Error # 10054, Connection reset by peer

The remote server or some other software is forcibly closing or resetting the established connection. This may be a problem with your network, firewall or AV configuration, the remote server is stopped or rebooted.

Ensure that the hostname or IP address of the remote server is correct and check if the remote server is reachable.

Socket error # 10055, No buffer space available

This error indicate that Windows has run out of socket buffers. The most common causes of this error are running a high number of applications simultaneously and insufficient system resources (memory or disk space).

Close unwanted programs that are running, restart the computer to free up resources. If you are backing-up to a cloud server, then reduce the number of threads to use from Cloud > Advanced settings page.

Socket error # 10060, Connection timed out

This is a connection timeout error, which means the remote server did not properly respond after a period of time. It generally suggests firewall or network issues e.g. a firewall may be permitting some commands/responses but blocking others or may be the hostname/port is incorrect.

Socket error # 10061, Connection refused

A connection to the server cannot be established as the remote server actively refused the connection. The common causes are the server is not running, incorrect connection parameters are used when establishing a connection (e.g. a wrong port number is used), a firewall or antivirus is blocking the connection.

Check if the server connection details are configured correctly and ensure the firewall is not blocking the connection.

Socket error # 10106, Service provider failed to initialize

This error can be caused by corrupted Windows system files, incomplete installation/uninstallation of applications or the computer is infected by a virus or malware.

Re-install SyncBack. Run a disk check and virus scan to detect and fix errors.

Socket error # 11001, Host not found

Check that the hostname or IP address has been entered correctly.

Socket error # 11002, Nonauthoritative host not found

This is a temporary error during hostname resolution, which means the hostname could not be resolved to an IP address. Try reconnecting later.