Client

ByteArrayOutputStream var4;
DataOutputStream var5;
try
	 	        {
	    			var4 = new ByteArrayOutputStream();
	    	        var5 = new DataOutputStream(var4);
	    			byte[] data3=getemail.getBytes("UTF-8");
		   	       	var5.writeInt(data3.length);
		   	       	var5.write(data3); 	
	    			Packet250CustomPayload var6 = new Packet250CustomPayload("iServerPacket", var4.toByteArray());
	 	        	PacketDispatcher.sendPacketToServer(var6);
	 	        }
	    		catch(Exception var7)
	    	    {
	    	        	var7.printStackTrace();
	    	    }

Packet Handing

public void onPacketData(INetworkManager manager,
		Packet250CustomPayload packet, Player player) {

	if (packet.channel.equals("iServerPacket")) {
            iHandler(packet);
		}
}
private void iHandler(Packet250CustomPayload packet) {
	DataInputStream packetrecv = new DataInputStream(new ByteArrayInputStream(packet.data));
	try
	{
    int length=packetrecv.readInt();
	byte[] passdata = new byte[length];
	packetrecv.readFully(passdata);
	String passstr=new String(passdata,"UTF-8");
	System.out.println(passstr);
    }
    catch(IOException ieo)
        {
        	ieo.printStackTrace();
        }

this source in packet handler can't print result

first of all: ALWAYS CLOSE THE STREAM. ALWAYS.

 

also you aren't specifying what to read, the Data(Output/Input)Streams comes with UTF handling. You could try to use that instead of reading fully. And you cannot throw a byte array into the stream and expect it to be received as a char array(String). If you want to handle raw byte arrays try using a byte buffer like so:

//for reading
byte[] b = data.read();
ByteBuffer.wrap(b).asCharBuffer().array().toString();

although you'd have to break it down to match the ByteBuffer formatting on input (UTF != charBuffer formatting). I'd just stick with DataOutputStream.writeUTF("yadda");