What is port 1433 used for?
Port 1433 is the default port of Microsoft SQL Server. Applications, reporting tools and administrators connect to it to run queries against a default database instance.
Only the default instance uses 1433. Named instances pick a dynamic port at start-up unless an administrator fixes one, which is why a firewall rule for 1433 alone is sometimes not enough. A database port open to the internet is a serious finding: it invites password guessing against database accounts and exposes the server to any flaw in the engine. Database servers belong on an internal segment, reachable only from the application servers that need them.
Is port 1433 TCP or UDP?
TCP. The database engine's default instance listens on TCP 1433. A second service, SQL Server Browser, answers on UDP 1434 to tell clients which port a named instance is using.
Is SQL Server on port 1433 encrypted?
It can be. SQL Server supports TLS for client connections, and the server can be set to force encryption so that no client connects without it. Encryption does not replace network controls: 1433 should still be reachable only from the application tier.
Port 1433 vs port 1434: what is the difference?
TCP 1433 is the database engine itself, for a default instance. UDP 1434 is the SQL Server Browser service, which only answers the question of which port a named instance listens on.
Which CompTIA exams list port 1433?
CompTIA lists port 1433 by number in the Network+ objectives; the A+ Core 1 port list does not include it.
- Network+ N10-009: objective 1.4 (Networking Concepts), listed as “Structured Query Language (SQL) Server, 1433”.
The quoted text is how the objectives document lists the port. The exam puts the port in a scenario, such as a firewall rule or a failed connection; it does not only ask for the number.
Check yourself: a practice question
Written by CertSprint for this page. It is not taken from any exam.
A web server in a screened subnet must query a SQL Server default instance on the internal network. Which firewall rule is the minimum needed?
- Allow TCP 1433 from the web server to the database server only
- Allow all ports from the internet to the database server
- Allow UDP 69 between the two servers
- Allow TCP 23 from the database server to the internet
Show the answer
A. Allow TCP 1433 from the web server to the database server only. A default instance listens on TCP 1433, and least privilege limits the rule to the one source that needs it.
Sources: IANA Service Name and Transport Protocol Port Number Registry: port 1433; Microsoft Learn: Configure the Windows Firewall to allow SQL Server access; Microsoft Learn: Configure SQL Server Database Engine for encrypting connections. The port number and how each exam lists it come from CompTIA's exam objectives, linked from the study plans above. The explanation and the question are CertSprint's own, checked against these sources on 12 November 2026.