Slave cannot connect to Master

I found the problem: in Jenkins Master Configuration, in Jenkins URL, instead of "localhost:8080", I put the IP of the server (http://[ip_server]:8080/) and now I can connect my slave to my master by using each way.

More specifically to Denis's answer, go to Manage Jenkins->Configure Systems->Jenkins Location : "Jenkins URL" and change "localhost:8080" to your Master's ip and port. (If you happened to change the port number).

Then we picked the choice of downloading the slave.jar and using the command prompt to connect the agent.

After installing the Jenkins slave.If your unable to load the Jenkins in the brwoser or not getting the jenkins start page follow these steps , directly paste this in your terminal.

firewall-cmd --permanent --new-service=jenkinsfirewall-cmd --permanent --service=jenkins --set-short="Jenkins Service Ports"firewall-cmd --permanent --service=jenkins --set-description="Jenkins service firewalld port exceptions"firewall-cmd --permanent --service=jenkins --add-port=8080/tcpfirewall-cmd --permanent --add-service=jenkinsfirewall-cmd --zone=public --add-service=http --permanentfirewall-cmd --reloadfirewall-cmd --list-all