hello, ive portfowared my server with the reborn gserver which it lets you port foward online, i can join using the client and putting my servers name in, other players that try to join they say it says the connection cannot be established, what can be the cause for this and how may i fix it  

http://lmgtfy.com/?q=port+forwarding


http://portforward.com/  

it comes with a gserver port foward so i use that >.< and players cant join it.  

In your GServer's console, does it mention something about UPNP not being able to forward the GServer port? If it does, you'll have to do it manually, by referring to the links I posted.