I have CoreFTP configured for localhost and the next code:
JSch.setLogger(new MyJschLogger()); //class for console output
Session session = jsch.getSession("user", "localhost", 21);
Properties config = new Properties();
config.put("StrictHostKeyChecking", "no");
session.setConfig(config);
session.setPassword("password");
session.connect();
when program achieves connect(), two messages appear at console output:
INFO: Connecting to localhost port 21
INFO: Connection established
...and nothing more happens. After some minutes, connection is closed by foreign host exception appears.
Why?
Thanks for all!
Port 21 is the normal port for FTP. JSch is only an SSH client, with support for SFTP in the ChannelSFTP class. JSch knows nothing about FTP (and SFTP is unrelated to FTP, other than by name and that it allows similar things).
You need to setup your server to use the SSH protocol (usually on port 22, but you can use any port, as long as you use the same port on the client). See the documentation - I think you have to check the SSH check box.
Also, if your code is nothing more than what you posted, then nothing more than connecting will happen. To transfer files, you will need to open a ChannelSFTP, and issue the right commands (e.g. call one or more of the put/get methods).
I also faced the similar issue:
"ERROR 2016-04-27 15:05:16,489 [CollectionThreadPool-0] com.dell.supportassist.collector.cli.executor.SSHExecutor: com.jcraft.jsch.JSchException: connection is closed by foreign host"
In my case, channel was getting closed randomly. And when we are trying to re-connect the channel then it was not re-connecting and failing.
This was happening due to looping logic while connecting, so I tried to connect the session without channel by calling method connectWithoutOpenChannel instead of connectinternal(). This resolved my issue.
Related
I have a setup where I use Flask-MQTT to connect my python Flask API to a Mosquitto broker. Whenever I run the Flask API with the development server all is well. But whenever I spin it up for production (using wsgi+nginx), the connection with Mosquitto is made, but everytime i try to publish something i get the following error:
Socket error on client <unknown>, disconnecting.
My app.ini has the processes configured to 1 (processes = 1)
My mosquitto.config has the allow_anonymous flag set to trye (allow_anonymous true)
I can't really seem to figure out what I'm doing wrong here...
Update:
So what i think is happening is that the Flask-uwsgi application is trying to connect to mosquitto more than once. There is a master process that connects with Mosquitto on initialize. Then there is a second process that is being used whenever input is given on the Flask app. I'm not sure, but I think Mosquitto only wants one connection at the time, therefor erroring on the second. So now i either need to:
A) Configure Mosquitto in a way that it accepts multiple connection from the same device
B) Configure Flask in a way that wil only use one single process (configuring processes = 1 is not enough, it will still spawn two processes)
99% of the time, a "Socket error on client <unknown>" is an authentication error. I don't know Flask, so I don't know where to point you at, but something in your code is either trying to pass a username/password that is not defined to Mosquitto, or its trying a TLS connection with an cert that Mosquitto doesn't like.
Alright, it turns I could've read that the whole multiple processes wouldn't work from the start at the official Flask-MQTT documentation. It sais right there in think letters:
Flask-MQTT is currently not suitable for the use with multiple worker
instances.
So I looked at my uwsgi app.ini file again closely and actually the answer is quite simple. I turned out i had a like in there master = true.. after I removed that it works like a charm.
So, I used the example on http://www.jcraft.com/jsch/examples/Sftp.java and I was trying to connect to ftp.secureftp-test.com.
That destination is a valid testing SFTP server (as mentioned in secureftp-test dot com/). I confirmed it by connecting to the server through nautilus. I also made sure that the password on my program was correct as well.
But, when I run the program and it hits session.connect(), it just says "INFO: Connection established" then it becomes quiet for a minute then it return:
"com.jcraft.jsch.JSchException: connection is closed by foreign host"
I am pretty sure that it got stuck in the while loop of the library but I do not know why. I tried it against my local ftp server and it also had the same problem.
During the quiet moment, I can type. But pressing enter does not send anything to the server.
Has anyone heard or seen the same problem?
Okay, it seems that secureftp-test.com is NOT an sftp server. That is ftps server.
What I did instead was creating my own sftp:
http://wiki.vpslink.com/Configuring_vsftpd_for_secure_connections_(TLS/SSL/SFTP)
Then run the example code but making sure that I have these lines before doing session.connect:
String knownHostsFilename = "/home/yourname/.ssh/known_hosts";
jsch.setKnownHosts(knownHostsFilename);
I'm studying Unix sockets programming. I made a time server that sends raw time data and a client for it that receives that data and converts it to local time.
When I run the server, connect a client to it (which causes both of them to do their job and shutdown) and then rerun the server, I get errno = 98 on bind() call. I have to change the port in the server's source code and recompile it to get rid of that error. When I run the server and connect to it again it's ok, after another rerun the situation repeats. But I can change back to previous port then. So I'm jumping from port 1025 to 1026 and vice-versa each debug run (which are very frequent, so this annoys a little).
It works like this: The server opens the listener socket, binds to it, listens to it, accepts a connection into a data socket, writes a time_t to it, closes the data socket and then closes the listener socket. The client opens a socket, connects to a server, reads data and closes the socket.
What's the problem?
Thanks in advance.
The sockets have a lingering time after they close. They may keep the port taken for a litte while after the execution of your application, so they may send any unsent data. If you wait long enough the port will be released and can be taken again for another socket.
For more info on Socket Lingering check out:
http://www.developerweb.net/forum/archive/index.php/t-2982.html
setsockopt and SO_REUSEADDR
errno 98 - Address already in use
Look into SO_REUSEADDR
Beej's guide to network programming
More details on what causes this:
http://www.serverframework.com/asynchronousevents/2011/01/time-wait-and-its-design-implications-for-protocols-and-scalable-servers.html
I have a Flex client using a Flash binary (TCP) socket for communication with a Java server. I have a localhost (Apache) server providing a crossdomain.xml file which is wide open just while I am testing.
My code successfully loads the policy file on startup.
I then connect the socket to the server without any difficulty and send a message and get a response. All good so far.
However, when I send a second message through the same socket I get a pause of about 12 seconds then a sandbox violation error:
Security Error: Error #2048: Security sandbox violation: file:///C:/apache_root/ttt1/ttt1.swf cannot load data from localhost:45455.
This is the same port and socket through which the first message succeeded.
I tried re-loading the policy file before every send, but I get the same result.
Any idea why this might be happening? I clearly have an open socket at one point. I am flushing the socket after each send and I tried doing that after each read as well, but the same result.
Thanks in advance
EDIT:
If I recreate the socket prior to every call my code works. I am struggling to believe that this is correct, but maybe there is a Socket setting I am missing.
As far as I know if you're doing binary sockets the crossdomain.xml is not loaded via http.
Have you checked your apache's access logs if the crossdomain is even queried?
You might get connection from flash via tcp from flash asking for the file on your java server (not using http. It just sends the string "" or similar). Look out for them. If you don't answer them within 3 seconds (or so) flash throws an sandbox violation.
The first thing you have to do when you want to make a socket connection is to load the policy file. This only has to be done once per load of the SWF.
Security.allowDomain(host);
Security.loadPolicyFile("xmlsocket://"+host+":"+port);
The request will be made on the assigned port(45455 in your case) your server will have to listen on that port for a request "<policy-file-request/>" without the quotes.
When that request is found then you need to return to the client the crossdomain.xml
with node <allow-access-from domain="*" to-ports="*" />
After the cross domain is sent you need to close the socket on the server side
On the client side you need to ignore the domain response as Flex will handle that however at that time you can reconnect to the socket server.
At this time you can do your data send/receive.
I have a feeling the reason it actually worked for you is because you were using the connection for the policy file to transmit your data before it timed out.
I would suggest reading up on the new style of crossdomain policies and also reading up on the protocol you are using for your socket server
I think it depends on the sandbox-policy you used in the compilation process of your swf not on your crossdomain.xml... maybe this docu helps you:Security sandboxes
But I'm not 100% sure
This sort of sounds like a cache problem. Perhaps you're pulling the first socket connection out of cache and the second one gets rejected because it's getting a 200 from the server.
You might want to add localhost to your flash security exceptions list for debugging. that will quiet the sandbox errors until you get your piece to it's production environment.
I am trying to open the COM1 port but I am getting this error message "Access to the port 'COM1' is denied". I am writing a program for sending SMS via .NET. I expect there could be an error, but the error "Access denied" should not be arisen. Please give me any solution. If port requires any access privileges then how can I do that?
First, make sure the serial port exists. Check the Device Manager; right-click on My Computer, select "Manage" from the context menu, select "Device Manager", expand "Ports Com & LPT". If Com1 is not listed, you will need to enable it in the BIOS.
If COM1 is there, then another program has left it open. Access to COM1 is exclusive; only one program can have it open at a time. Fax software or a modem could have it open, or you could have left it open yourself.
This is easy to do. If you work on a program that opens the port and forget to close it, or if an error occurs and the program terminates without closing the port, this is the message you will get the next time you try to open COM1. Only the program that opened the port can close it. "Catch" or "Finally" blocks are good places to close the port and prevent this.
There's probably something else using COM1 (auto sync programs tend to be quite bad at grabbing COM ports as soon as they become available).
Try downloading PortMon and it will tell you exactly what's using the port.
Since you tagged this asp.net, are you trying to access the port with multiple threads? (as in on a request, accessing the port, creating the connection, sending data, closing connection, closing the port?
If you are, this is also a problem. If I am not mistaken, only one thread can access a com port at a time. You will need to write some code to ensure that only one thread is trying to access the port at a given time. Typically I would suggest a queue and a worker for that queue that does the job.
There is probably another program using the serial port. Have you tried firing up hyperterminal?
If you are trying to use ASP.Net under IIS there account running the website may not have permissiongs to the device, as well as, there could also be conflicting thread/multi-access issues. Something to consider would me to write a service that manages requests for the COM port and then talk to that service from ASP.Net. This will allow for split permissions and controlled single access to the COM port. Any other hack has the potential of causing lots of problems.