Minecraft Server

Ive been having problems with my minecraft server where my friends or anyone outside my wifi can join just fine but if youre connected to my wifi that the server is connected to, youll be able to connect sometimes but not others.
 
Uhm... I don't know what it is, but I can tell you the following:
- If your local computers all have internet access and you still can't connect to the server locally, that suggests the problem has to do with how internal IPs are being assigned in your LAN. For example, I would check to make sure you have a fixed internal IP assigned to your server computer and that your server.properties file has that IP assigned so that it's binding correctly. If one day, your computer gets 192.168.1.12 and another it gets 192.168.1.14, then your other computers, trying to connect to 192.168.1.12 will fail, but your remote friends will still be able to connect. So that coincides with your case.
- If your other local computers are failing to also connect to the internet when they can't get to the server, then it's a connectivity problem that may have to do with your router. Maybe your server computer is able to connect to the internet because it's directly plugged to the router, but the WiFi is not working properly. I think this is not very likely, but could be.
- Finally, if you just want a quick solution, when remote players can connect but your LAN players can't, that tells me that you can quickly save the day by having your local players connect via your public address instead of your local address. It'll give them unnecessary latency, but it should work if you can't wait
- Oh, and there's another trick you can use sometimes. You can use the client as a server. Just open your game for LAN and look at what it says in the console chat, something like "Server connected at port 46282", for example. Then go to your router's menu and forward that port number to your client/server-to-be's local IP. Now you can have your remote players connect to your client as a server. The same trick can be use to have local players who can't find your client in the LAN connect to it by brute force.

Good luck!