The default instance of Microsoft SQL Server — the TDS client protocol, on Windows and Linux alike.
SQL Server's default instance is assigned TCP 1433 at installation and clients speak the Tabular Data Stream protocol to it. Named instances use dynamic ports instead and rely on the SQL Server Browser on UDP 1434 to be found, so 1433 specifically means "the default instance", including SQL Server on Linux and in containers. TCP 1434 is separately used by the Dedicated Administrator Connection for the default instance. It is one of the most heavily scanned ports on the internet because a reachable SQL Server is a direct path to a whole database.
Do not expose
A database engine on a public IP is a credential-spraying and CVE target with the entire dataset behind it; bind it to a private network and reach it over a VPN or tunnel.
$ sqlcmd -S TARGET,1433 -U sa -Q "SELECT @@VERSION"Seen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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