How can I change the port in Node.js?

Question

Node.js

Error occurs
C:\proekt>gulp
[19:29:22] Using gulpfile C:\proekt\gulpfile.js
[19:29:22] Starting 'styles'...
[19:29:22] Finished 'styles' after 17 ms
[19:29:22] Starting 'express'...
[19:29:22] Finished 'express' after 91 ms
[19:29:22] Starting 'livereload'...
[19:29: 22] Finished 'livereload' after 67 ms
[19:29:22] Starting 'watch'...
[19:29:23] Finished 'watch' after 43 ms
[19:29:23] Starting 'default'.. [ 19:29:23
] Finished 'default' after 4.11 ?s
events.js:154
throw er; // Unhandled 'error' event
^
Error: listen EADDRINUSE 127.0.0.1:80
at Object.
at exports._exceptionWithHostPort (util.js:879:20)
at Server._listen2 (net.js:1236:14)
at listen (net.js:1272:10)
at net.js:1381:9
at GetAddrInfoReqWrap.asyncCallback [ as callback] (dns.js:63:16)
at GetAddrInfoReqWrap.onlookup [as oncomplete] (dns.js:82:10)