It looks like you are trying to connect with mods that you shouldn't have on your client. If you want to connect to the regular TFC servers, you should only have TFC installed and maybe a few client-side mods like Optifine and Journey map. Connecting with a mod pack like TechnodeFirmaCraft won't work for the regular TFC servers.
Here's what the server log shows:
Code:
[08:09:48] [Server thread/WARN]: Failed to handle packet for /<IP>:57583
org.bukkit.plugin.messaging.ChannelNameTooLongException: Attempted to send a Plugin Message to a channel that was too large. The maximum length a channel may be is 16 chars (attempted 20 - 'ImmersiveEngineering.
at org.bukkit.plugin.messaging.StandardMessenger.validateChannel(StandardMessenger.java:446) ~[minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at org.bukkit.plugin.messaging.StandardMessenger.dispatchIncomingMessage(StandardMessenger.java:419) ~[minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.PlayerConnection.a(PlayerConnection.java:1971) ~[minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.PacketPlayInCustomPayload.a(PacketPlayInCustomPayload.java:39) ~[minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.PacketPlayInCustomPayload.handle(PacketPlayInCustomPayload.java:51) ~[minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.NetworkManager.a(NetworkManager.java:186) ~[minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.ServerConnection.c(ServerConnection.java:81) [minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.MinecraftServer.v(MinecraftServer.java:734) [minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.DedicatedServer.v(DedicatedServer.java:289) [minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.MinecraftServer.u(MinecraftServer.java:584) [minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:490) [minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [minecraft_lobby01.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
[08:09:48] [Server thread/INFO]: Gotlag666 lost connection: Internal server error
[08:09:48] [Server thread/INFO]: Gotlag666 left the game.