Program: 96730
Project: 96730
Buggy source:
public void processDataPacket(RaknetDataPacket dataPacket){
  this.lastPacketReceived=System.currentTimeMillis();
  if (dataPacket.getSequenceNumber() - this.lastSequenceNum > 1) {
    for (int i=this.lastSequenceNum + 1; i < dataPacket.getSequenceNumber(); i++) {
      this.queueNACK.add(i);
    }
  }
  this.lastSequenceNum=dataPacket.getSequenceNumber();
  this.queueACK.add(dataPacket.getSequenceNumber());
  if (dataPacket.getEncapsulatedPackets().isEmpty()) {
    return;
  }
  for (  EncapsulatedPacket epacket : dataPacket.getEncapsulatedPackets()) {
    PEPacket packet=PEPacket.fromBinary(epacket.buffer);
    if (packet == null) {
      continue;
    }
switch (packet.pid()) {
case PEPacketIDs.PING:
      PingPongPacket pkPong=new PingPongPacket();
    pkPong.pingID=((PingPongPacket)packet).pingID;
  this.send(pkPong,0);
break;
case PEPacketIDs.CLIENT_CONNECT:
if (this.loginStage != 0) {
break;
}
this.clientSessionID=((ClientConnectPacket)packet).sessionID;
ServerHandshakePacket pkServerHandshake=new ServerHandshakePacket();
pkServerHandshake.port=(short)(this.remotePort & 0xFFFF);
pkServerHandshake.session=this.clientSessionID;
pkServerHandshake.session2=0x04440BA9L;
this.loginStage=1;
this.send(pkServerHandshake);
break;
case PEPacketIDs.CLIENT_HANDSHAKE:
if (this.loginStage != 1) {
break;
}
this.loginStage=2;
break;
case PEPacketIDs.LOGIN_PACKET:
if (this.loginStage != 2) {
break;
}
LoginPacket packetLogin=(LoginPacket)packet;
this.username=packetLogin.username;
this.translator=TranslatorProvider.getByPEProtocolID(this,packetLogin.protocol1);
if (!(this.translator instanceof BaseTranslator)) {
LoginStatusPacket pkLoginStatus=new LoginStatusPacket();
pkLoginStatus.status=2;
this.send(pkLoginStatus);
this.disconnect("String_Node_Str");
break;
}
LoginStatusPacket pkLoginStatus=new LoginStatusPacket();
pkLoginStatus.status=0;
this.send(pkLoginStatus);
this.getLogger().info("String_Node_Str");
Matcher matcher=patternUsername.matcher(this.username);
if (!matcher.matches()) {
this.disconnect("String_Node_Str");
break;
}
this.loginStage=3;
this.setPlayer(new PlayerProfile(this.username,UUID.nameUUIDFromBytes(("String_Node_Str" + this.username).getBytes(StandardCharsets.UTF_8))));
break;
case PEPacketIDs.CLIENT_DISCONNECT:
this.statusActive=false;
break;
default :
if (this.loginStage != 3) {
break;
}
if (!(this.translator instanceof BaseTranslator)) {
break;
}
this.dServer.getThreadPool().submit(new ProcessPEPacketTask(this,packet));
break;
}
}
}

Fixed version (ground truth):
public void processDataPacket(RaknetDataPacket dataPacket){
  this.lastPacketReceived=System.currentTimeMillis();
  if (dataPacket.getSequenceNumber() - this.lastSequenceNum > 1) {
    for (int i=this.lastSequenceNum + 1; i < dataPacket.getSequenceNumber(); i++) {
      this.queueNACK.add(i);
    }
  }
  this.lastSequenceNum=dataPacket.getSequenceNumber();
  this.queueACK.add(dataPacket.getSequenceNumber());
  if (dataPacket.getEncapsulatedPackets().isEmpty()) {
    return;
  }
  for (  EncapsulatedPacket epacket : dataPacket.getEncapsulatedPackets()) {
    PEPacket packet=PEPacket.fromBinary(epacket.buffer);
    if (packet == null) {
      continue;
    }
switch (packet.pid()) {
case PEPacketIDs.PING:
      PingPongPacket pkPong=new PingPongPacket();
    pkPong.pingID=((PingPongPacket)packet).pingID;
  this.send(pkPong,0);
break;
case PEPacketIDs.CLIENT_CONNECT:
if (this.loginStage != 0) {
break;
}
this.clientSessionID=((ClientConnectPacket)packet).sessionID;
ServerHandshakePacket pkServerHandshake=new ServerHandshakePacket();
pkServerHandshake.port=(short)(this.remotePort & 0xFFFF);
pkServerHandshake.session=this.clientSessionID;
pkServerHandshake.session2=0x04440BA9L;
this.loginStage=1;
this.send(pkServerHandshake);
break;
case PEPacketIDs.CLIENT_HANDSHAKE:
if (this.loginStage != 1) {
break;
}
this.loginStage=2;
break;
case PEPacketIDs.LOGIN_PACKET:
if (this.loginStage != 2) {
break;
}
LoginPacket packetLogin=(LoginPacket)packet;
this.username=packetLogin.username;
this.translator=TranslatorProvider.getByPEProtocolID(this,packetLogin.protocol1);
if (!(this.translator instanceof BaseTranslator)) {
LoginStatusPacket pkLoginStatus=new LoginStatusPacket();
pkLoginStatus.status=2;
this.send(pkLoginStatus);
this.disconnect("String_Node_Str");
break;
}
LoginStatusPacket pkLoginStatus=new LoginStatusPacket();
pkLoginStatus.status=0;
this.send(pkLoginStatus);
this.getLogger().info("String_Node_Str");
Matcher matcher=patternUsername.matcher(this.username);
if (!matcher.matches()) {
this.disconnect("String_Node_Str");
break;
}
this.loginStage=3;
this.setPlayer(new PlayerProfile(this.username,UUID.nameUUIDFromBytes(("String_Node_Str" + this.username).getBytes(StandardCharsets.UTF_8))));
break;
case PEPacketIDs.CLIENT_DISCONNECT:
this.onDisconnect();
break;
default :
if (this.loginStage != 3) {
break;
}
if (!(this.translator instanceof BaseTranslator)) {
break;
}
this.dServer.getThreadPool().submit(new ProcessPEPacketTask(this,packet));
break;
}
}
}