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Kavin, I guess you must have found some other solution or moved on by now. However, I just came across a requirement that led me to this page.
I looked through the somewhat smuckish responses on this page and many others but could not find a simple to use Telnet client at all.
I spent a little bit of time and wrote a simple client on top of Commons Net's solution. Please forgive the System.out and System.err in the code, I got it to barely work.
public static void main(String[] args) throws Exception {
SimpleTelnetClient client = new SimpleTelnetClient("localhost", 2323);
client.connect();
String result = client.waitFor("login:");
System.out.println("Got " + result);
client.send("username");
result = client.waitFor("Password:");
System.out.println("Got " + result);
client.send("password");
client.waitFor("#");
client.send("ls -al");
result = client.waitFor("#");
System.out.println("Got " + result);
client.send("exit");
Not sure if it will help you anymore, but perhaps it could be a starting point for others.
import java.io.InputStream;
import java.io.PrintStream;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.LinkedBlockingQueue;
import org.apache.commons.net.telnet.EchoOptionHandler;
import org.apache.commons.net.telnet.InvalidTelnetOptionException;
import org.apache.commons.net.telnet.SuppressGAOptionHandler;
import org.apache.commons.net.telnet.TelnetClient;
import org.apache.commons.net.telnet.TerminalTypeOptionHandler;
public class SimpleTelnetClient {
static class Responder extends Thread {
private StringBuilder builder = new StringBuilder();
private final SimpleTelnetClient checker;
private CountDownLatch latch;
private String waitFor = null;
private boolean isKeepRunning = true;
Responder(SimpleTelnetClient checker) {
this.checker = checker;
boolean foundWaitFor(String waitFor) {
return builder.toString().contains(waitFor);
public synchronized String getAndClearBuffer() {
String result = builder.toString();
builder = new StringBuilder();
return result;
@Override
public void run() {
while (isKeepRunning) {
String s;
try {
s = checker.messageQueue.take();
} catch (InterruptedException e) {
break;
synchronized (Responder.class) {
builder.append(s);
if (waitFor != null && latch != null && foundWaitFor(waitFor)) {
latch.countDown();
public String waitFor(String waitFor) {
synchronized (Responder.class) {
if (foundWaitFor(waitFor)) {
return getAndClearBuffer();
this.waitFor = waitFor;
latch = new CountDownLatch(1);
try {
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
return null;
String result = null;
synchronized (Responder.class) {
result = builder.toString();
builder = new StringBuilder();
return result;
static class TelnetReader extends Thread {
private final SimpleTelnetClient checker;
private final TelnetClient tc;
TelnetReader(SimpleTelnetClient checker, TelnetClient tc) {
this.checker = checker;
this.tc = tc;
@Override
public void run() {
InputStream instr = tc.getInputStream();
try {
byte[] buff = new byte[1024];
int ret_read = 0;
ret_read = instr.read(buff);
if (ret_read > 0) {
checker.sendForResponse(new String(buff, 0, ret_read));
} while (ret_read >= 0);
} catch (Exception e) {
System.err.println("Exception while reading socket:" + e.getMessage());
try {
tc.disconnect();
checker.stop();
System.out.println("Disconnected.");
} catch (Exception e) {
System.err.println("Exception while closing telnet:" + e.getMessage());
private String host;
private BlockingQueue<String> messageQueue = new LinkedBlockingQueue<String>();
private int port;
private TelnetReader reader;
private Responder responder;
private TelnetClient tc;
public SimpleTelnetClient(String host, int port) {
this.host = host;
this.port = port;
protected void stop() {
responder.isKeepRunning = false;
responder.interrupt();
public void send(String command) {
PrintStream ps = new PrintStream(tc.getOutputStream());
ps.println(command);
ps.flush();
public void sendForResponse(String s) {
messageQueue.add(s);
public void connect() throws Exception {
tc = new TelnetClient();
TerminalTypeOptionHandler ttopt = new TerminalTypeOptionHandler("VT100", false, false, true, false);
EchoOptionHandler echoopt = new EchoOptionHandler(true, false, true, false);
SuppressGAOptionHandler gaopt = new SuppressGAOptionHandler(true, true, true, true);
try {
tc.addOptionHandler(ttopt);
tc.addOptionHandler(echoopt);
tc.addOptionHandler(gaopt);
} catch (InvalidTelnetOptionException e) {
System.err.println("Error registering option handlers: " + e.getMessage());
tc.connect(host, port);
reader = new TelnetReader(this, tc);
reader.start();
responder = new Responder(this);
responder.start();
public String waitFor(String s) {
return responder.waitFor(s);
–
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