what is dns port


DNS protocol transport

DNS primarily uses the User Datagram Protocol (UDP) on port number 53 to serve requests. DNS queries consist of a single UDP request from the client followed by a single UDP reply from the server.

What port is used for DNS?


A DNS server listens for requests on port 53 (both UDP and TCP). So all DNS requests are sent to port 53, usually from an application port (>1023).

How do I find my DNS port number?

Web-browsers use the URL protocol prefix (http://) to determine the port number (http = 80, https = 443, ftp = 21, etc.) unless the port number is specifically typed in the URL (for example “http://www.simpledns.com:5000” = port 5000). The port is usually fixed, for DNS it’s 53. Port numbers are defined by convention.

The Domain Network System (DNS) protocol helps Internet users and network devices discover websites using human-readable hostnames, instead of numeric IP addresses.
DNS and some other services work on both the protocols. … DNS uses TCP for Zone transfer and UDP for name queries either regular (primary) or reverse. UDP can be used to exchange small information whereas TCP must be used to exchange information larger than 512 bytes.
In OSI stack terms, DNS runs in parallel to HTTP in the Application Layer (layer 7). DNS is in effect an application that is invoked to help out the HTTP application, and therefore does not sit “below” HTTP in the OSI stack. DNS itself also makes use of UDP and more rarely TCP, both of which in turn use IP
How to check which application is using which port
  1. Open the command prompt – start » run » cmd or start » All Programs » Accessories » Command Prompt.
  2. Type netstat -aon. | ..
  3. If the port is being used by any application, then that application’s detail will be shown. …
  4. Type tasklist. …
  5. You’ll be shown the application name that is using your port number.
  6. TCP port 53 is used for domain transfers; the only reason I can see it being open is if the OP is running a DNS server. DNS servers also listen on UDP port 53 to accept queries from client resolvers
    A protocol is a set of rules that governs the communications between computers on a network. … IP/IPX (Network Layer) TCP/SPX (Transport Layer) HTTP, FTP, Telnet, SMTP, and DNS(combined Session/Presentation/Application Layers)



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