Develop Reference

How to check when connection is established, if minecraft player's session is valid as original player?

I challenged myself to create a minecraft server with the proviso that most of the plugins I will use will be just mine. I have already made many different plugins from shops to various minigames. Now I have decided to code my own login registration plugin. Basically everything is already functional and ready, but I would like to add one feature there. This feature is that when a player connects to the server (warez), my plugin checks the player's session to see if it is original (I mean that player have bought game and he is logged throught original mojang launcher with valid mojang session. Players should connecting to server in warez mode (not logged in, using not official launcher)). I don't just mean the name as mentioned here, but his mojang session. In short, whether it is logged in via the original launcher with its e-mail and password.
I absolutely don't know how verifying the originality of players works, I know that mojang has an API but I don't know if it offers such a possibility. I would also like to know if the client is sending a hash from the UUID or sessionID to the server, which can be compared with the mojang API, or I don't know.
UPDATE:
I found these two articles:
1) https://wiki.vg/Protocol#Login
2) https://wiki.vg/Protocol_Encryption#Authentication
From this articles I roughly understood that during the connection of the client I will send the server ID and ciphers together with the server and then the subsequent hash on which they will agree will send the client via POST to the mojang servers and my server should then ask from the mojang if it is logged in on my server the client.
UPDATE2
I thought of the following:
If I programmed my own proxy in the phenomenon to which players would connect and this proxy would reproduce everything to the server. Thus, I would be able to let in who I would like to go and I can also do cross-checks via the mojang page with the server ID and hash. But it would be 3-rd party software, it would not be a plugin.
Modify the spigot itself, by that I mean do the above somewhere at the SSLServerSocket level, where the spigot server receives all the socket and the data from them. There, if I code the bridge over which the data would pass, I am also able to agree with the client SERVER ID, calculate a hash and verify it from the mojang server. But it would still not be within the plugin but in the servers.
Override some of the deep parts of the server mentioned above from the plugin. The plugin would replace some parts of the server after loading.
Now my questions is, how to replace some mentioned parts of the server from plugin? Is good idea to try use reflection (i am noob, with reflection) and replace some functions with my functions, that would calling back to spigot low level code?
Thank you very much for any advice.
Have a nice day.
PS: Sorry for my bad english.

public boolean isCracked(ProxiedPlayer player) {
String name = player.getName();
UUID actualUUID = player.getUniqueId();
String actualUUIDStr = uuid.toString();
String offlineUUIDStr = getMd5("OfflinePlayer:"+name);
if(offlineUUIDStr.equals(actualUUIDStr)) {
return true;
}
return false;
}
// Taken from https://www.geeksforgeeks.org/md5-hash-in-java/
public static String getMd5(String input)
{
try {
// Static getInstance method is called with hashing MD5
MessageDigest md = MessageDigest.getInstance("MD5");
// digest() method is called to calculate message digest
// of an input digest() return array of byte
byte[] messageDigest = md.digest(input.getBytes());
// Convert byte array into signum representation
BigInteger no = new BigInteger(1, messageDigest);
// Convert message digest into hex value
String hashtext = no.toString(16);
while (hashtext.length() < 32) {
hashtext = "0" + hashtext;
}
return hashtext;
}
// For specifying wrong message digest algorithms
catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e);
}
}
}

FTPSClient, What values to give for Remote and Local

I am new to FTPSClient i trying to connect to a FTPS created in my laptop. i don't exactly what some of the methods working and their parameter meaning.
For example,
In my code i have created a FTPSClient as below:
FTPSClient ftps =new FTPSClient();
Then connected to a server use connect() method with ip address.
ftps.connect("172.xx.xx.xxx");
After every step i will check the reply code using.
ftps.getReplyCode();
In the below code i know that
username = system username
password = the password to login
ftps.login(username, password);
In the my system in Internet Information Service(IIS). Created an ftp server with ssl and given the below directory to share.
C:\Users\karan-pt2843\Desktop\FTPS
Want to send the file in below directory to the server.
D:\sam.txt
Now i want to store a file in the server in the given above directory and i tried using
remote="";
local="";
InputStream input;
input = new FileInputStream(local);
ftps.storeFile(remote, input);
input.close();
I don't know what value to give for remote and local. please help me with the values to give on them and the what happens internal.

// Use passive mode as default because most of us are
// behind firewalls these days.
ftps.enterLocalPassiveMode();
...
String remote = "samFromClient.txt"; //Place on FTP
String input = "D:/sam.txt" //Place on your Client
//Your FTP reads from the inputstream and store the file on remote-path
InputStream input = new InputStream(new FileInputStream(input));
ftps.storeFile(remote, input);
input.close();
ftps.logout();
...
Taken from: Apache example

How to programmatically connect internet via datacard with AT commands?

I have a datacard ZTE MF190. I want to use AT commands to register in 2G or 3G and access internet via datacard. Found this article about how to make data call:
AT+cgatt=1
AT+CGDCONT=1,”IP”,”epc.tmobile.com” //I used my operator PDP context
AT+CGACT=1,1
But ping from OS terminal shows 100% package loss.
I've tried on Ubuntu 14 and Windows 7.
How can I connect internet with AT commands using datacard on Ubuntu?
UPDATE
I gave bounty to #tripleee's answer because it's more full than first one and answered all my questions. But I'm not satisfied with answers, so I'll answer my own question in a week.
In my answer I'll show how to handle this process with Java. So, please do not move this question to other Stack Exchange websites.

Creating a connection between the card and your provider is not sufficient. You need some mechanism for creating a network interface out of this connection, and set up your network stack to route packets over this interface.
Traditionally, the pppd daemon has been a popular choice for this task. You would create a "chat script" with the commands for establishing a data call (these days, pppd might come packaged with a suitable canned script) and the daemon would handle the entire process of placing the call, authenticating, setting up a network interface over the circuit, and configuring the system to route packets over it, as well as configuring DNS etc to use it for resolver queries, etc.

I tried to sniff USB port but on this case dashboard can not connect because of busy port
It is certainly possible. See this question
Found this article about how to make data call
What that article is about is how to set up the call, not how to make it.
After you made correct setup, connect to internet with this command:
ATD*99***1#
UPDATE1: After a bit of research I believe that article was written only to promote their software and has no practical use. In reality dialing is made with pppd or wvdial
UPDATE2: We discussed ways to solve the problem in a chat room (in Russian). It turned out cnetworkmanager will be the way to go

As far as I know wvdial uses ppp daemon to connect to the internet using modem. wvdial is preinstalled on desktop version of Ubuntu.
wvdial uses a config file located /etc/wvdial.conf. Let's edit this file. Type in your terminal
sudo nano /etc/wvdial.conf
and you will see something like this
[Dialer Defaults]
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2
Stupid Mode = yes
ISDN = 0
Modem Type = Analog Modem
New PPPD = yes
Phone = *99#
Modem = /dev/ttyUSB2
Username = ''
Password = ''
Baud = 9600
Dial Timeout = 30
Dial Attempts = 3
Explanation of all keys you can find in wvdial.conf(5) - Linux man page. If you need to change your provider dial number, username, password or any other information about connection and device you can change file content and save it.
There are 3 serial ports for ZTE MF190. Normally it's ttyUSB0, ttyUSB1 and ttyUSB2. And in my case ttyUSB2 is for internet connection. It would not work on other ports. So you need to find the right serial port for your modem.
There is an automatic configurator which edits wvdial.conf file, sets serial port baud rate etc. Since it is not always configure correctly I would not recommend to use it:
sudo wvdialconf /etc/wvdial.conf
It would be better if you configure wvdial manually.
Now, when your device connected and wvdial configured to work with device, you can execute this line from terminal:
wvdial
You will see a lot of lines. But if you see those lines - you have succeeded.
local IP address XX.XX.XX.XX
remote IP address XX.XX.XX.XX
primary DNS address XX.XX.XX.XX
secondary DNS address XX.XX.XX.XX
Now, how we can use it in programming? I'll provide some code to work with it on Java. You can use this code to dial.
public int dialer() {
// status for debug. If status == 4 then you connected successfully
int status;
// create process of wvdial
ProcessBuilder builder = new ProcessBuilder("wvdial");
try {
// start wvdial
final Process process = builder.start();
// wvdial listener thread
final Thread ioThread = new Thread() {
#Override
public void run() {
try {
final BufferedReader reader = new BufferedReader(
new InputStreamReader(process.getErrorStream()));
// wvdial output line
String line;
while ((line = reader.readLine()) != null) {
// if "local IP address" line detected set status 1
if (line.contains("local IP address")) {
status = 1;
}
if (line.contains("remote IP address")) {
status = 2;
}
if (line.contains("primary DNS address")) {
status = 3;
}
if (line.contains("secondary DNS address")) {
status = 4;
}
}
reader.close();
} catch (final Exception e) {
}
}
};
// start listener
ioThread.start();
// wait 6 secs and return status. Some kind of timeout
Thread.sleep(6000);
} catch (Exception e) {
}
return status;
}
And here is a disconnector method. All you need is to kill wvdial process and thread will be destroyed:
public boolean disconnect() {
ProcessBuilder builder = new ProcessBuilder("pkill", "wvdial");
try {
builder.start();
return true;
} catch (IOException e) {
return false;
}
}

How to handle (failed) login attempts with Smack XMPP API

I'm developing a chat server based on XMPP and Smack API, which connects to an Openfire server (Hosted by a friend who is also developing this with me).
So, I started programming it just a few days ago (Netbeans on OS X 10.8), and today I went on to the connection and login aspects.
I can login perfectly with the right choice of username+password :P but I don't know how to handle an invalid login attempt and let the app show a message and then allowing the user to retry.
Here's my code, which fires after user has pressed a button in my Swing JForm:
(Note: XMPPConnection object is already created in another class, and the connection has been made to the server. You can see I'm calling the object from that another class)
private void btnIniciarSesionActionPerformed(java.awt.event.ActionEvent evt) {
String Usuario = txtUsuario.getText();
String Password = new String (pwdContrasena.getPassword());
if (Usuario.equals("") || Password.equals("")){
// Missing data
JOptionPane.showMessageDialog(null, "Missing data");
}
else{
//Try to login
try{
Proyecto_chat.conexion.login(Usuario, Password, "x");
}
catch (XMPPException ex){
Logger.getLogger(Ventana_login.class.getName()).log(Level.SEVERE, null, ex);
// Problem
}
if (Proyecto_chat.conexion.isAuthenticated() == true){ //Login has been successful
jLabel1.setVisible(false);
System.out.println("Authenticated as " + Usuario);
JOptionPane.showMessageDialog(null, "Authenticated as " + Usuario);
//Exit login window and carry on
}
else{
JOptionPane.showMessageDialog(null, "login error");
}
}
}
Should I play with that exception I'm getting? ->
SEVERE: null
SASL authentication DIGEST-MD5 failed: not-authorized:
at org.jivesoftware.smack.SASLAuthentication.authenticate(SASLAuthentication.java:337)
at org.jivesoftware.smack.XMPPConnection.login(XMPPConnection.java:203)
at proyecto_chat.Ventana_login.btnIniciarSesionActionPerformed(Ventana_login.java:159)
at proyecto_chat.Ventana_login.access$100(Ventana_login.java:15)
at proyecto_chat.Ventana_login$2.actionPerformed(Ventana_login.java:73)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
(...) more lines that I think are not critical for this
As passwords are stored in plain text (University project, so it doesn't matter) for simplifying changing them from inside the application, I can connect to the database (PostgreSQL in remote server) from the client computer, and check the passwords and only do 'conexion.login' if user&pass matches, but that would be... you know... wrong
After looking around on the web with no luck, I decided to head over here, ask, go to sleep and wake up next morning with some suggestions ;)
Help shall be appreciated

Not sure if I understand what you are asking but if it's "How can I determine the reason for a failed login attempt with Smack?" then here is my answer:
You have to evaluate the (XMPP)Exception's message string as of Smack 3.2.2 if you want to determine the reason for the failed login. These message strings that distinguish between the various failure reasons are currently hard-coded in the source, which is usually not a good idea.
A while ago I have created SMACK-416 "Improve Exceptions on connect() and login()" to address this issue. The idea is to replace the hard-coded strings/failure reasons with a class hierarchy. But it sure will take a few months until this is implemented (and maybe a few weeks/months/years until it is released).

Actually, the main problem was that when I tried to login using an invalid username/password, some exception was thrown (As well as an information display that I set up), but the application wouldn't let me log in again (As if I corrected my data and clicked the button again).
I finally solved this by placing the .connect() right behind the .login() method, and calling .disconnect() in case a bad login was made, so the server would be reconnected every time the user tried to log in .
This might not be the ideal approach, but I find it easy and do-able. Thanks for helping!

Sending messages from pc via mobile phone using java

I am working on an application, using java, that has the following features:
User connects his mobile to a PC using a usb cable or bluetooth.
User types a message on his PC (in the textfield provided by my software).
User types a phone number (in a textbox provided by my software).
User clicks the send button.
Then, the software should send the message to the specified phone number and appropriate charges should be applied to my mobile balance. In other words, I am directing my mobile through my software to send message to a specified number.
How shall i do that? Is core java sufficient for this purpose or i have to use j2me or is there any particular java framework that would be suitable for this?

One option is to connect the phone to the pc using serial link (COM). Need to configure the phone connected physically by USB or Bluetooth in order to appear in a COM (serial) port.
Then you need to create an application for PC (Java or whatever can open serial ports) that opens the COM port used by the phone and send the proper AT commands. Serial port can be opened by JavaComm 2.0 Win32 or more recently RxTx.
Open the serial port and write and read command by writing and reading bytes, in the same way a socket.
Then create a visual application that let user set the information like phone number for destination, text...
You need Java SE or whatever language allows you to create visual applications and opening serial ports (Java, .NET, Python...).
Some links about AT commands by serial port in Windows: 1, 2, 3.
Another option could be using native API from the mobile OS through a socket, but seems complex and using AT commands and serial port should work for all phones and the only problem is connecting the phone by serial over USB or BlueTooth and managing the serial port.

This is highly dependent on the Mobile OS you're using. Are you using Windows Mobile, Android OS, BlackBerry OS?
If you're using Android, then you should use the built in SmsManager to do that. The SmsManager can do the following:
Manages SMS operations such as sending data, text, and pdu SMS messages.
Update:
Since you're using Symbian OS, then check out the documentation for more information on sending SMS messages. I assume that you can figure out the rest (i.e. how to get the text fields for the number and the message, etc.)
Here is an example from the Symbian OS documentation:
public boolean sendSms(String number, String message){
boolean result = true;
try {
//sets address to send message
String addr = "sms://"+number;
// opens connection
MessageConnection conn = (MessageConnection) Connector.open(addr);
// prepares text message
TextMessage msg =
(TextMessage)conn.newMessage(MessageConnection.TEXT_MESSAGE);
//set text
msg.setPayloadText(message);
// send message
conn.send(msg);
conn.close();
} catch (SecurityException se) {
// probably the user has not allowed to send sms
// you may want to handle this differently
result = false;
} catch (Exception e) {
result = false;
}
return result;
}
The above snippet came from the guide on "How to Send Text SMS in Java ME"