I am trying to find somw Windows based tools that can help me validate TCP and UDP connection on remote machines.
My Problem (just one use case):
At work, I manage many clustered servers that I run load tests against. In order to get a rich test, I use Jmeter-Plugins which provides a Server agent that opens a TCP socket on port 4444 on a target remote machine: http://code.google.com/p/jmeter-plugins/wiki/PerfMonAgent
There are many times when I setup a new load test farm, that either the network, or the server configuration, or the ServerAgent itself can have issues and thus not allowing a Load test client to access that TCP connection.
The issue I have is that I dont know what part of the system is broken.
What I think I need:
I would like to know how I can open a TCP (not HTTP with cUrl), connection to a remote server to validate that the network allows the connection, as well as the Server firewall allows the given TCP connection to be accessed remotely.
What I have looked:
These are some of the tools I have looked at so far:
Nmap http://nmap.org
Ncat http://sourceforge.net/projects/nmap-ncat/
TCP/IP Builder http://www.drk.com.ar
Zenmap 6.01 and nmap might do the job I want, but some machines where not accessible to Zenmap when I know 100% that the server was accessible via HTTP, so that was strange.
I have looked at many tools and either they:
Dont allow remote connections
Dont seem to want to connect to a TCP socket
Or I dont understand the tools to accomplish the validation I stated above.
I would greatly appreciate all comment and suggestions to help with this re-occurring problem I face.
Mick,
Firebind.com can do what you'd like to do. Firebind is an Internet based server that can listen on any of the 65535 UDP or TCP ports. It uses a java based client to send traffic to and from the server from your machine.
Carl
www.firebind.com
Related
I'm using BOOST-ASIO for a simple echo client-server (there is a separate link for the client and server). When I try to run the server I use this async_tcp_echo_server 4000. For the client I use blocking_tcp_echo_client #.#.#.# 4000 (with #.#.#.# as the ip address). I'm on XP-SP3 with my computer connected to my wireless dsl modem using a usb card. After a few seconds on the client side I get this error:
Exception: connect: A connection attempt failed because the connected party did
not properly respond after a period of time, or established connection failed be
cause connected host has failed to respond
Any ideas what it could be? I turned off my firewall including the windows firewall and still I get no response. Could my port be in the incorrect range? Do I need to include a computer name to specify the machine on the network( there are other machines on the network sometimes active)? I did try running this on another computer directly connected to the dsl modem and same issue. I did ping my address and that did work for 4/4 packets.
It could be a variety of issues. Thus, it can be worthwhile to use lower level networking tools, such as netcat to serve a port on the server, and try connecting with netcat from the client side. This can help simplify the problem by removing any potential problems introduced by an application's network programming code. If the problem is identified as being a network issue, then there are a few things to check:
Verify firewall exceptions on the server.
Verify firewall exceptions in the server's network gateway.
If the server and client are on different networks, with the client trying to connect to the server's external IP, then verify that the server's gateway knows what traffic to route to the server. This may require setting up rules, such as port forwarding, in the routing device.
If the server and client are on the same network, but the client is trying to connect to the server through the network's external IP, then verify that the gateway supports looping back internal traffic destined to the external IP.
Use a network analyzer tool, such as Wireshark, to verify that the time to live field in the packets is high enough that it will not be discarded.
you could try
$ telnet server-ip 4000
from your client and see if it is possible to establish the tcp connection.
This is part programming, part sysadmin, so please excuse me if you feel that this should be over on serverfault.
I have an application that is not SOCKS aware and that we need to use through a firewall. We cannot modify the application to have SOCKS support either.
At the moment, we do this by aliasing the IPs the application talks to the loopback adapter on the host, then creating SSH tunnels out to another host. The IP's the application uses are hardcoded. Our SSH connections look like:
ssh -L 1.2.3.4:9999:1.2.3.4:9999 user#somehost
Where 1.2.3.x are aliases on the loopback.
So the application connects to the open port on the loopback, which gets sent out to the SSH host and onto the real 1.2.3.4.
It works, but the problem is that this application connects to quite a few IPs ( 50+ ), so we end up with 50 ssh connections out from the box.
We've tried to use several 'proxifying' apps, like tsocks and others but have had alot of issues with them ( the app is running on OS X and tsocks doesn't work so well, even with the patches )
Our idea was to write a daemon that listened on all interfaces on the specified port - it would then take the incoming packets from the application, scrape the packet info ( dst IP, port, payload ), recreate the packet and proxify it through a single SSH SOCKS connection ( ssh -D 1080 user#somehost ). That way, we only have 1 SSH connection that all the ports are being proxied through.
My question is - is this feasible? Is there something that I'm missing here? I've been combing through pfctl, ipfw, iptables docs, but I don't see any option to do it through those and this doesn't seem like it'd be the most difficult thing to code. It would recreate the packet based on the original destination IP and port, connect to the local SOCKs proxy and resend the packet as if it were the original application, but now with SOCKS support.
If I'm missing something that someone knows about that already does this, please let me know. I don't know socket programming or SOCKs too well, but this doesn't seem like it'd be too big of a project to tackle, but I'd like some opinions if I'm biting off way more that I should.
Thanks
If your application could add SOCKS client support, you can simply ssh -D lock_socks_port remote_machine, which will open up the local *lock_socks_port* as a SOCKS server at localhost, which can then connect to any host accesible by the remote machine.
Example: imagine you are using an untrusted wifi network without encryption. You can simply launch ssh -D 1082 home, and then configure your web browser to use localhost:1080 as SOCKS server. Of course, you need a SOCKS-enabled client. All the traffic would appear as coming from your gateway, and the connection would be opaque to those snooping the wifi.
You can also open a single ssh client with an indefinite number of LocalForward requests, which would be tunneled on top of a single ssh session.
Moreover, you can add ssh connections to an already-established ssh connection by using the ControlMaster and ControlPath options of ssh.
I am splitting an application into a tray application and a Windows Service and I want to use TCP to communicate between the two*. They will both be running on the same machine.
My question is do firewalls block TCP communication between applications running on the same machine? I want to know whether firewalls are something I need to worry about when testing.
(*note that I want to use TCP instead of named pipes for communication because the apps might one day run on separate computers but that will be far in the future)
The primary objective of the firewall is to control the incoming and the outgoing network traffic! Firewall's are designed to work on IP or PORT basis.
So yes, it is 100% capable of blocking connection on same machine.(I guess you are using Class A IP [127.x.y.x] address used mainly for loopback testing and interprocess communication on the local computer).
Some firewall are preconfigured not to block local machine connection while other are configured to block them. But either way a firewall can be configured to allow/deny such connection.
I have to test the value from client to server using different protocols (Tcp , UDP , Sctp).
Please guide how it can be possible. Is there any way in windows to change the protocol or is there anyway to find it by using software like packet tracer .
Thanks
While the question is not entirely clear, it sounds as though your interested in seeing the information sent between the client and the server when each of those protocols is used.
Windows does not provide a built in utility to view packet data but it can be viewed using a packet analyser such as Wireshark.
In order to see the values sent by each protocol you must run a client for each of the protocols and use it to connect to the server for that protocol. If you don't have a server to connect to, you may need to run one on your local machine.
You can narrow down the data captured to just the protocol you're interested in using a filter in Wireshark If you don't know the protocol being used, you can filter by the port number used for that connection which can be established using the netstat command.
You may need to use netstat -b to show you which programs are using which ports.
If you just have to generate packets using different protocols then the tool like netcat can also help. It supports TCP and UDP and has been ported to windows .
If I create a c++ server/client application, the port I used to communicate does it need to be open on the router of the server and client machine
Or what other approach could I take? the client computer needs to receive information from the server but I am not able to have any ports opened because it is on a school network....
[edit]
Hmm My setup is a php page running on a server say when I press hello, the server makes a ssh connection through php and sends shell commands to the machine. The server is running off of a school server which I do have ssh access to and run all my things from there. The client computer will be my pc running off of the school wifi which is not connected to the server. The server will try to make a ssh connection to the public ip of my computer running off of the school wifi(no ports open/can ssh out but no ssh in). Will these methods you mention make this possible, in particular the connect.c since I can't run putty off of the server, and the connect.c I could call from the php.
The choice of language is highly irrelevant here.
There don't need to be ports 'open' on any router, unless your traffic must pass through it. On normal peer hosts in the same network (or subnet) there would hardly be any firewall policy, not even in schools.
Technically it is possible for the switch to block peer-2-peer traffic (meaning traffic not destined to the outgoing gateway), but that is not very usual.
Of course, if the school doesn't allow outbound (WAN) traffic on most ports, tough luck, and they're absolutely right :)
You can look at
ssh (with tunnels -L, -D and -R options, perhaps -o GatewayPorts on)
stunnel
connect.c
http-tunnel
All very readily googled
To establish a TCP/IP connection, only the server port needs to be accessible by the client. The connection is full-duplex, therefore data can flow from the client to the server and vice-versa.
If you are using UDP for your application, which is a connection-less protocol, what happens depends heavily on the firewall or router and whether it performs connection tracking for your service or not.
Unless you provide some additional information on your service and the network setup on both the client and the server side, we cannot provide more concrete information.