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https://issues.apache.org/jira/browse/SSHD-744?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15997074#comment-15997074
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Miron Aseev commented on SSHD-744:
----------------------------------
No biggie. Thanks.
> An SSH client receives an echo as a response from the server
> ------------------------------------------------------------
>
> Key: SSHD-744
> URL: https://issues.apache.org/jira/browse/SSHD-744
> Project: MINA SSHD
> Issue Type: Question
> Affects Versions: 1.4.0
> Reporter: Miron Aseev
> Priority: Minor
>
> I'm trying to integrate my Java application with a device which provides a
> custom protocol over SSH.
> The whole point of this protocol is about exchanging XML documents back and
> forth. It can be described with the following steps:
> # a client connects to the server
> # the client sends an XML document which contains the request data
> # the client waits for the XML document which contains a response data from a
> server
> # the server receives the XML document that was sent by the client and sends
> the response XML document back to the client
> # the client receives the XML response from the server and closes the
> connection
> The recommended way to send requests to this device is to use `cat` and `ssh`
> tools. Here's a simple example:
> {code}
> cat example.xml | ssh <user_id>@<device_ip>
> {code}
> where `example.xml` is a file that contains an XML document with the request
> data.
> Calling directly 'cat' and 'ssh' via Runtime.exec would be very problematic
> because this approach has a lot of drawbacks. So, I decided to implement this
> protocol using MINA SSHD library.
> The problem I've run into is I receive my own request as a response from the
> server. So there's some kind of echoing stuff going on, I think.
> For example, when I send this XML document as a request to the server:
> {code}
> <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
> <xg-request>
> <action-request>
> <action-name>test</action-name>
> </action-request>
> </xg-request>
> {code}
> I receive the following data as a response:
> {code}
> Last login: Wed May 3 07:33:43 2017 from ip
> Header
> <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
> <xg-request>
> <action-request>
> <action-name>test</action-name>
> </action-request>
> </xg-request>
> {code}
> The funny this is when I send the same request via cat and ssh (the example I
> mentioned above), I receive the correct response from the device.
> Here's an excerpt from my application:
> {code}
> public class Test {
> private static final long AWAIT_TIMEOUT = TimeUnit.SECONDS.toMillis(5);
> private static final String XML_PAYLOAD_HEADER = "<?xml";
> public void init() throws IOException, JAXBException {
> try (SshClient client = initSshClient();
> ClientSession session =
> initClientSession(client, "test", "localhost", 22, "pass")) {
> sendRequest(session);
> }
> }
> private static SshClient initSshClient() {
> SshClient client = SshClient.setUpDefaultClient();
> client.start();
> return client;
> }
> private ClientSession initClientSession(SshClient client, String user,
> String host, int port,
> String password) throws IOException
> {
> ClientSession session =
> client.connect(user, host, port).verify(AWAIT_TIMEOUT).getSession();
> session.addPasswordIdentity(password);
> session.auth().verify(AWAIT_TIMEOUT);
> return session;
> }
> private void sendRequest(ClientSession session) throws IOException {
> try (PipedOutputStream out = new PipedOutputStream();
> PipedInputStream channelIn = new PipedInputStream(out);
> PipedOutputStream channelOut = new PipedOutputStream();
> PipedInputStream in = new PipedInputStream(channelOut);
> BufferedReader reader = new BufferedReader(new
> InputStreamReader(in));
> BufferedWriter writer = new BufferedWriter(new
> OutputStreamWriter(out));
> ClientChannel channel = initClientChannel(session, channelIn,
> channelOut)) {
> String xmlRequest = ""; // Here goes a real XML document;
> writer.write(xmlRequest);
> writer.newLine();
> writer.flush();
> String response = readFully(reader);
> }
> }
> private static ClientChannel initClientChannel(ClientSession session,
> InputStream input,
> OutputStream output) throws
> IOException {
> ClientChannel channel = session.createChannel(Channel.CHANNEL_SHELL);
> channel.setIn(input);
> channel.setOut(output);
> channel.setErr(new ByteArrayOutputStream());
> channel.open().verify(AWAIT_TIMEOUT);
> return channel;
> }
> private static String readFully(BufferedReader reader) throws IOException {
> StringBuilder builder = new StringBuilder();
> String line;
> boolean foundXmlPayload = false;
> while ((line = reader.readLine()) != null) {
> if (foundXmlPayload && line.isEmpty()) {
> break;
> }
> builder.append(line);
> if (!foundXmlPayload && builder.indexOf(XML_PAYLOAD_HEADER) != -1) {
> foundXmlPayload = true;
> }
> }
> return builder.toString();
> }
> }
> {code}
> Any suggestions would be greatly appreciated.
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