Such Network, Very Packet, Much Handler For So 1.7.2 / 1.7.10

gistfile1.java

/// PacketHandler.java ///
public class PacketHandler
{
  public static PacketHandler instance;
  public final SimpleNetworkWrapper net;
  
  public static void init()
  {
    instance = new PacketHandler();
    instance.net = NetworkRegistry.INSTANCE.newSimpleChannel("CHANNEL_NAME_USE_YOUR_MODID");
    registerPacket(0, TestPacket.class, TestPacket.TestMessage.class);
  }
  
  private void registerPacket(int index, Class packet, Class message)
  {
    net.registerMessage(packet, message, index, Side.CLIENT);
  }
}

/// TestPacket.java ///
public class TestPacket implements IMessageHandler<TestMessage, IMessage>
{
  // This calls when a client or a server receives a message, after fromBytes()
  @Override
  public IMessage onMessage(FlyMessage message, MessageContext ctx)
  {
    if (ctx.side.isClient())
    {
      System.out.println("Hello, I sent you a message with a byte. Byte = " + message.exampleByte);
    }
    // You can return reply message if you want, null for nothing
    return null;
  }
  
  public static class TestMessage implements IMessage
  {
    private byte exampleByte;
		
		@Override
		public void fromBytes(ByteBuf buf)
		{
			this.exampleByte = buf.readByte();
		}
		
		@Override
		public void toBytes(ByteBuf buf)
		{
			buf.writeByte(exampleByte);
		}
		
		public FlyMessage setByte(byte par1)
		{
			this.exampleByte = par1;
			return this;
		}
  }
}

/// Sending a packet ///

// always check for "instanceof" when casting something
if (player instanceof EntityPlayerMP)
{
  PacketHandler.instance.net.sendTo(new TestMessage().setByte(255), (EntityPlayerMP)player);
}

/**
 * you can send packets from client to server the similar way
 */