I set variables host and port instead of setting the 'address' variable tuple in socket.py. I was unable to get 'address' as a tuple to work. I do not believe this is the issue, but I thought I should state this up front.
FYI, my goal is an integrations project, and I believe I isolated socket.py as the problematic code. socket.py is not creating a listener on the remote server. I run the python script on my client, and my server address is 192.168.1.130 port 7879.
I think socket.py is the problem, because I do not receive the expected print statements back through the console that socket.py is attempting to create a socket. In addition, I can RDC to the server, disable ufw (yes I know this is a bad idea), create a tcp listener, push data through the client socket to the server socket, and verify this with netcat.
Am I mistaken that I should be able to parameterize socket.py with nothing more than a host and port and be able to create a socket connection? I am happy to provide more detail from logs, but I thought I should start with a very high level overview.
Answer: More investigation needed. I think socket.py does not create the remote connection with socket(),bind(),listen() statements; instead simply looks for a listener on the remote server with a connect() statement. This is entirely my misunderstanding given I did not dive into the details of the socket.py code. I figured this out because the service running on the remote server creates the listener, but the service itself on the remote server is what is not properly starting.
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I have an application with a server written in F# and serve web files using suave. I remote login using powershell into another machine in the network to run the application (The application is also in one of the network drives). I do that because that machine have access to third party APIs needed for the server. Now when I do [IPAddress_Of_Remote_Machine]/[html_file] or [name_of_pc]/[html_file] then chrome is waiting forever and doesn't ever return the webpage. This wasn't happening before and I ran into this problem recently. I opened a different port and used it instead of the default one 80. This made things work but the problem keeps showing up after a couple of days. I don't think it's a firewall issue but I'm clueless to why this is happening.
When running netstat -an, this is what I get (I hid the IP address):
As you can see all of the connections are either in CLOSE_WAIT or ESTABLISHED but not LISTENING. All of these TCP connections is probably because I have PhantomJS and two other APIs running in the application as well. However the loop back address is also open on the same port 5959:
I'm not sure what is difference between these two but when using PortQryUI to query the remote server it returns a success!
I have already made an inbound rule for port 5959 on the server so it should be allowed. The web page is stuck at Waiting for [name_of_pc]. Also, sometimes this problem disappears and everything works fine.
What is the potential problem behind this? Why would this happen all of a sudden?
UPDATE:
I re-ran the application today and it's working correctly. It could be that something is dynamically set within the firewall? Not really sure what is going on. The machine I'm running the server on has a bunch of applications running on it as well so maybe there is an external process that is affecting it?
I made a hello world app with Suave and deployed it on the network drive to test if it's going to work. I opened inbound rule for port 6001
Then I ran the app:
However, it's still not working and this time it says the site cannot be reached when I do: http://[name_of_pc]:6001.
Moving this to an answer so that it can be closed:
Could you post the bindings section of your suave cfg? I'm guessing you know where that is since you are using a non-standard port but if you need don't, search for HttpBinding. I suspect you will find it pointing to 127.0.0.1 which is not good enough for remote access. You could try changing it to 0.0.0.0 or to the server's actual IP address. I would try 0.0.0.0 first for the flexibility it provides
I establish a TCP connection between my server and client which runs on the same host. We gather and read from the server or say source in our case continuously.
We read data on say 3 different ports.
Once the source stops publishing data or gets restarted , the server/source is not able to publish data again on the same port saying port is already bind. The reason given is that client still has established connection on those ports.
I wanted to know what could be the probable reasons of this ? Can there be issue since client is already listening on these ports and trying to reconnect again and again because we try this reconnection mechanism. I am more looking for reason on source side as the same code in client sides when source and client are on different host and not the same host works perfectly fine for us.
Edit:-
I found this while going through various article .
On the question of using SO_LINGER to send a RST on close to avoid the TIME_WAIT state: I've been having some problems with router access servers (names withheld to protect the guilty) that have problems dealing with back-to-back connections on a modem dedicated to a specific channel. What they do is let go of the connection, accept another call, attempt to connect to a well-known socket on a host, and the host refuses the connection because there is a connection in TIME_WAIT state involving the well-known socket. (Stevens' book TCP Illustrated, Vol 1 discusses this problem in more detail.) In order to avoid the connection-refused problem, I've had to install an option to do reset-on-close in the server when the server initiates the disconnection.
Link to source:- http://developerweb.net/viewtopic.php?id=2941
I guess i am facing the same problem: 'attempt to connect to a well-known socket on a host, and the host refuses the connection'. Probable fix mention is 'option to do reset-on-close in the server when the server initiates the disconnection'. Now how do I do that ?
Set the SO_REUSEADDR option on the server socket before you bind it and call listen().
EDIT The suggestion to fiddle around with SO_LINGER option is worthless and dangerous to your data in flight. Just use SO_RESUSEADDR.
You need to close the socket bound to that port before you restart/shutdown the server!
http://www.gnu.org/software/libc/manual/html_node/Closing-a-Socket.html
Also, there's a timeout time, which I think is 4 minutes, so if you created a TCP socket and close it, you may still have to wait 4 minutes until it closes.
You can use netstat to see all the bound ports on your system. If you shut down your server, or close your server after forking on connect, you may have zombie processes which are bound to certain ports that do not close and remain active, and thus, you can't rebind to the same port. Show some code.
If you telnet to the ip address 192.43.244.18 port 13, you'll get the current time.
well, if I'm not wrong, this is simply a server socket. But there's one thing strange: how's this socket always listening?
If I take a PHP page and program sockets in there, I still have to request for the page first in order to activate the server socket, but this one isn't associated with any pages, and even if a make a perl script, I still have to request for that in order to run the server socket!
My question is: how can I make such a thing - an always listening socket - on a webhost (any language will do)?
You can run the process that's listening on the socket as a daemon (Linux) or service (Windows), or just a regular program really (although that's less elegant).
A simple place to begin would be http://docs.oracle.com/javase/tutorial/networking/sockets/clientServer.html which teaches you how to make a simple serversocket in Java that listens for a connection on a specific port. The program created will have to be run at all times to be able to accept the connections.
I have a simple node.js client and server programs running on one machine and when I try to connect to the server with second instance of client program simultaneously I get EADDRINUSE, Address already in use error. Is it possible to have two or more TCP based socket client connections (created with createConnection) to one server (created with createServer) on the same machine, or only one client program can be connected to the server at the same time?
Yes, it's possible. Infact, very common. Many applications open dozens, or hundreds of connections to the same server. It sounds like your client program is binding on a port. Only the server should be binding on a port. You should verify.
The client will usually use a random port between 1024-65535, as assigned by your OS. You don't need to worry about it. Since the client is initiating a connection to the server, the server port must unique to one program. Which is why your problem signifies you are trying to start the server twice. Please see http://www.tcpipguide.com/free/t_TCPIPClientEphemeralPortsandClientServerApplicatio.htm
For example http://www.utorrent.com/testport?port=12345
How does this work? Can the server side script attempt to open a socket?
There are many ways of accomplishing this through server-side scripting. As #Oded mentioned, most server-side handlers are capable of initiating socket connections on arbitrary ports, and most of those even have dedicated port-scanning packages/libraries (PHP has one in the PEAR repository, Python's 'socket' module makes this type of tasks a breeze, etc...)
Keep in mind that on shared host platforms, socket connections are typically disabled for security purposes.
Another way that is also very easy to accomplish is to use a command-line port-scanner such as nmap from your server-side script. i.e in PHP, you would do echo ``nmap -p $port $ip\
The server side script will try to open a connection on the specified port to the originating IP.
If there is no response (the attempt will timeout), this would be an indication that the port is not open.
The server can try, as #Oded said. But that doesn't ensure the receiver will respond.
Typically, something like this happens:
The URL request contains instructions about which port to access. The headers that your browser sends include information about where the request is originating from.
Before responding to the request, the server tries to open a port and checks if this is successful. It waits a while before timing out.
The webpage is rendered dynamically based on the results of this test.
The response is returned to you containing the results.
Sometimes steps (2) and (3) will be replaced with an AJAX callback, which allows the response to return sooner.