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The cURL project
Network and protocols
Install curl
Source code
Build curl
Command line basics
Command line options
Options depend on version
URLs
Scheme
Name and password
Host
Port number
Path
FTP type
Fragment
Browsers' address bar
Many options and URLs
Connection reuse
Parallel transfers
URL globbing
List options
Config file
Passwords
Progress meter
Using curl
HTTP with curl
FTP with curl
Using libcurl
HTTP with libcurl
Bindings
libcurl internals
Index
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Port number
Each protocol has a "default port" that curl will use for it, unless a specified port number is given. The optional port number can be provided within the URL after the host name part, as a colon and the port number written in decimal. For example, asking for an HTTP document on port 8080:
curl http://example.com:8080/
With the name specified as an IPv4 address:
curl http://127.0.0.1:8080/
With the name given as an IPv6 address:
curl http://[fdea::1]:8080/
The port number is an unsigned 16 bit number, so it has to be within the range 0 to 65535.

TCP vs UDP

The given port number is used when setting up the connection to the server specified in the URL. The port is either a TCP port number or a UDP port number depending on which actual underlying transport protocol that is used. TCP is the most common one, but TFTP and HTTP/3 use UDP.
URLs using the file:// scheme cannot have a port number.
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