Telnet login validation.

Question

HI,
I have a Java GUI app that telnets to a unix box and executes some commands. Everything works fine if the login/password is correct, but I don't really have a solution to check for login failure messages. The program need to determine whether the login was successfull or not. One way that I tought of was to look for the return string from the server and if it say "Login invalid", or "Account locked by .." or simillar messages, then the login failed. But this solution is not really what I'd like to use, because first I don't know what are all the login error messages that the server throws, and also whether these messages are universal.
Any help is appreciated.
Thanks.

Answer 1

I am using telnet source from javatelnet.org (javassh.org). I doesn't really give me a solution to my problem. The code assumes that the user can see the return string from the telnet app and determine what to do next. Here is the code:
public void connect() throws NetworkException
try
     LogPane.writeMedic("Connecting to " + serverName + " for " + username);
     rpcSession.connect(serverName, port);
     rpcSession.login(username, password);
rpcSession.setPrompt(PROMPT);
     rpcSession.send("export PS1='" + PROMPT + "'"));     
     rpcSession.waitfor(PROMPT);
catch (IOException e)
     //          LogPane.writeError("Error! Connecting to " + serverName);
               throw new NetworkException("Error! Connecting to " + serverName);
     //     e.printStackTrace();
login code from rpcSession:
public synchronized void login(String username, String password) throws IOException
byte[] b = new byte[256];
int n = 0;
waitfor("login:");
     send(username);
     waitfor("Password:");
     send(password);
The program waits for "login" and "password" and send their values and then it waits for the prompt, it only works if the login is successfull.