Cant join servers or worlds

[Mincelad]

My friends recently got a Technic modded server and i got everything downloaded fine and all is well. However the thing is whenever i try to join the server it spends about 20 minutes loading or logging in and then eventually it will say something along the lines of "The connection was forcibly closed by a remote host" and ill be taken back to the join screen. Or sometimes the game will just crash. The same occurs on single player worlds when i attempt them. Is this just my pc being shitty or is there something i can do to fix this? (Also sorry if i posted this on the wrong forum/page im new to this stuff and am still sorting it all out, if theres any more information needed for this let me know!)