I have a webserver running on my mac, and it happens to already be running on port 8080, which is jenkins default port, so i need to change it….

I found a good stackoverflow on this, and want to repost for myself, in case stack overflow ever goes away.

cd /Applications/Jenkins 
sudo vi winstone.properties

Add httpPort=9999 to the file.

To see all the options you can put in there type java -jar jenkins.war –help

run 

java -jar jenkins.war from /Applications/Jenkins.

Your port will be changed. jenkins.war picks up config options from ./winstone.properties by default.

now go to a browser and try http://localhost:9999