[MrRandom]

Look on your router, some have a setting called "wireless isolation" which prevents wireless clients from contacting each other.

Can't find that kind of setting in the router page :/

What is the make and model of the router?

Modem Telecom AG plus

[nickr]

Can any of your wireless clients communicate with others?

Can the web browser on your phone see the kodi web page?

[MrRandom]

Can any of your wireless clients communicate with others?

Can the web browser on your phone see the kodi web page?

Yes my phone can open the kodi page.
As for the first question, if you're asking if the other devices on the same wifi can ping my mac, then no they can't.

[-Jay-]

Can any of your wireless clients communicate with others?

Can the web browser on your phone see the kodi web page?

Yes my phone can open the kodi page.
As for the first question, if you're asking if the other devices on the same wifi can ping my mac, then no they can't.

So, when you said your firewall is off on the mac, you turned off the MAC firewall? Do you also have Norton or some other port blocking software installed?

Also, you don't have any other webserver running do you? Apache? etc? What type of error do you see when you go to the webserver from a remote computer?

See what happens when you go to http://locahost:8080 (I believe you said your kodi webserver was running on port 8080) on the kodi mac?

[-Jay-]

Also, check the MAC in the network settings. This may sound really silly but, make sure that the MAC is on the same subnet, has the same gateway, dns server, etc as the rest of your network. Make sure of the wireless network name. I have accidentally been connected to the wrong wireless network before. In other words, my modem (since it is from Comcast) has it's own wireless network that anyone that has a comcast account can connect to. I have been connected to that wireless before and not realized it. Make sure the SSID on the phone and the MAC are the same.

[MrRandom]

Can any of your wireless clients communicate with others?

Can the web browser on your phone see the kodi web page?

Yes my phone can open the kodi page.
As for the first question, if you're asking if the other devices on the same wifi can ping my mac, then no they can't.

So, when you said your firewall is off on the mac, you turned off the MAC firewall? Do you also have Norton or some other port blocking software installed?

Also, you don't have any other webserver running do you? Apache? etc? What type of error do you see when you go to the webserver from a remote computer?

See what happens when you go to http://locahost:8080 (I believe you said your kodi webserver was running on port 8080) on the kodi mac?

Same subnet, has the same gateway, dns server, same SSID, no mac or internet firewalls on, no webservers that i know (never even heard the name web server till yesterday), not sure about norton or those kinda things but i don't recall installing any antivirus. And when i check http://localhost:8080 my mac says webpage not avaible.

[-Jay-]

Well, you have to open http://localhost:8080 while kodi is running on that machine. There seems to be a more important issue though if the other computers on your network cannot ping that MAC.

When you open the System Preferences and go to Network, there will be a list of network connections on the left. How many are there and which ones say connected? There should only be one. The one that is connected, click on it and make sure it is the same IP address that you are attempting to ping. Is this a DHCP or Static assigned address? Also go to the Proxies Tab and make sure Web Proxy is not checked. This is a pretty odd situation.

Something else to check, if the connection is a static connection, go to the router and verify that there isn't an entry in the DMZ. Sometimes when an IP address is assigned to the DMZ, the router will isolate that IP from the rest of the network. If it is in the DMZ, I would remove it, unless you have a specific reason that it is facing the outside world.