I am developing a program that makes a request to a private IP address, to fetch data, which I can access only by being connected to that network.
And I have a database that is behind a vpn (other private IP), and I need to send that previous data to that database.
My computer is windows 10 and has two network cards, I can successfully connect to each network independently.
But the question is how can I make my computer stay connected to both networks at the same time and the described process works.
I appreciate if anyone can provide me with information on whether this is possible at the operating system configuration level. Or should it be something software development as such?
i have a big problem. I need tranfer a lot of files by a server to another server, but the second server isnt a local server. If i tranfer by a local server i cant 100mbs but if i send for another server out the speed is 2mbs. my network is 1gbs. I use a command line 7z.
If your servers are (as you wrote) on the same network and connected through the same line you are most likely to have a network connection problem.
I've often seen that the duplex settings of network cards are not set up correctly which leads to a lot of collisions.
Check your network card settings and try to force for example 100mbps full duplex.
I work for a company where this happens daily when trying to connect IBM network cards with Cisco switches. Have a look here how to set up duplex settings: https://superuser.com/questions/86581/how-do-you-check-the-current-duplex-value-of-a-network-card-set-to-auto-negotiat.
If this doesn´t help you might be better off asking at superuser.com
I wrote a tool running on a system (Win7) with two network interfaces, each linked to a different subnet, each with its own gateway which is then linked to two separate distant networks (there are outgoing firewalls after each gateway). I’m initiating outgoing TCP connections via both NICs by using Socket.Bind (before doing Connect) to each relevant NIC’s IP address. First NIC is working fine, but for the second NIC, I’m getting SocketException: “A socket operation was attempted to an unreachable network”.
My original understanding was that since sockets are bound to concrete NIC’s local endpoint, which has its gateway defined, the connection should be routed to this gateway and therefore should work. However, it seems that source IP address is ignored and the routing is working according to local routing table (i.e. second NIC’s connect request goes to first, default, network and being rejected because it has wrong subnet).
Adjusting local routing tables helps, but it makes me wonder about the whole reasoning behind ability of the socket to bind to specific local IP.
Doing some extra reading, I found out that, indeed, there’s such thing as “source IP routing”, but it is disabled in Windows by default (via DisableIPSourceRouting registry setting), due to security reasons, as described, e.g. here:
http://msdn.microsoft.com/en-us/library/ff648853.aspx
http://www.bloggersbase.com/disableipsourcerouting/
Questions:
If my original understanding was correct (i.e. Socket.Bind should be enough) – why it is not working without modifying routing tables?
If my understand was NOT correct (i.e. Socket.Bind is ignored and routing is used) – what’s the point of having Socket.Bind? Why doing it at all?
Also, I’d like to understand better, what is the actual risk of having source IP routing enabled (preferably with example of a possible exploit)?
Any ideas of solving the requirement without manually modifying local routing table will be greatly appreciated.
Many thanks.
OK, after some reading, here are some high-level explanations on what's happening. I still need to verify the below conclusions in my system. Apparently, local binding is typically ignored when selecting network interface. Instead, routing table is used for this. However, in Strong Host Model (default for Vista and newer, non-existant in XP), source IP is used as a 'constraint' in the routing table lookup.
Brief explanation about strong host model vs. weak host model:
http://technet.microsoft.com/en-us/magazine/2007.09.cableguy.aspx
Explanation on what's different in XP vs newer Windows versions in respect to the above:
http://blogs.technet.com/b/networking/archive/2009/04/24/source-ip-address-selection-on-a-multi-homed-windows-computer.aspx
stupid problem. I get those from a client connecting to a server. Sadly, the setup is complicated making debugging complex - and we run out of options.
The environment:
*Client/Server system, both running on the same machine. The client is actually a service doing some database manipulation at specific times.
* The cnonection comes from C# going through OleDb to an EasySoft JDBC driver to a custom written JDBC server that then hosts logic in C++. Yeah, compelx - but the third party supplier decided to expose the extension mechanisms for their server through a JDBC interface. Not a lot can be done here ;)
The Symptom:
At (ir)regular intervals we get a "Address already in use: connect" told from the JDBC driver. They seem to come from one particular service we run.
Now, I did read all the stuff about port exhaustion. This is why we have a little tool running now that counts ports and their states every minute. Last time this happened, we had an astonishing 370 ports in use, with the count rising to about 900 AFTER the error. We aleady patched the registry (it is a windows machine) to allow more than the 5000 client ports standard, but even then, we are far far from that limit to start with.
Which is why I am asking here. Ayneone an ide what ELSE could cause this?
It is a Windows 2003 Server machine, 64 bit. The only other thing I can see that may cause it (but this functionality is supposedly disabled) is Symantec Endpoint Protection that is installed on the server - and being capable of actinc as a firewall, it could possibly intercept network traffic. I dont want to open a can of worms by pointing to Symantec prematurely (if pointing to Symantec can ever be seen as such). So, anyone an idea what else may be the cause?
Thanks
"Address already in use", aka WSAEADDRINUSE (10048), means that when the client socket prepared to connect to the server socket, it first tried to bind itself to a specific local IP/Port pair that was already in use by another socket, either an active one or one that has been closed but is still in the FD_WAIT state. This has nothing to do with the number of ports that are available.
I'm having the same issue on a Windows 2000 Server with a .Net application connecting to a SQL Server 7.0. There's like 10 servers with the same configuration and only one is showing this error several times a day. With a small test program I'm able to reproduce the error by just establishing a TCP connection on the SQL Server listening port. Running CurrPorts (http://www.nirsoft.net/utils/cports.html) shows there's still plenty of available ports in range 1024-5000.
I'm out of ideas and would like to know if you've found a solution since you've posted your question.
Edit : I finally found the solution : a worm was present on the server (WORM_DOWNAD.A) and exhausted local ports without being noticed.
I often run into problems where I can't get something to connect to something else. I usually forget to check something obvious. Can you help with:
A tip/technique for diagnosing a connection issue
The name of a tool or application that can help (and the situation in which it's useful)
I know the question is a little non-specific, but hopefully the answers can form a useful starting point for anybody who's stuck trying to get computers/programs talking to each other.
Please can you give one answer per answer so the best ones can be voted up.
Simple checks to run when debugging network problems:
Has each machine got an IP address, Go to command prompt and run ipconfig. Key things to check here are the interfaces and ensuring the appropriate ones have IP addresses.
Check both machines IP addresses are in the same range and subnet if you are running it on an internal or Virtual network.
Try pinging each machine from the other to see if they can communicate with each other. Note that some firewalls will block ping requests.
If Pinging fails then check to see if firewalls are active. If the communication is within a 'safe' internal network then try disabling the firewalls and re-pinging.
If the connections are over a wireless network then check signal strength.
If pinging fails and you are connecting through several networks then try running a tracert to see at which will may show you where on the network the connection is failing.
If you are able to ping but not connect then check firewall settings and network connection settings. Windows 2000+ has the capability of setting port an ip access on a connection properties.
Try drawing a network diagram of the connections to help in visualising the problem.
If you are connecting through routers, firewalls and loadbalancers then check that all devices are not tied to any specific ip addresses and that the IP address redirection (if in place) is correct. Also check any NAT logs to see if connections are being received and properly re-directed.
Wireshark
Latest versions of ProcMon
netstat
Wireshark www.wireshark.org
Wireshark is a network protocol analyzer for Unix and Windows.
Features:
Deep inspection of hundreds of protocols, with more being added all the time
Live capture and offline analysis
Standard three-pane packet browser
Multi-platform: Runs on Windows, Linux, OS X, Solaris, FreeBSD, NetBSD, and many others
Captured network data can be browsed via a GUI, or via the TTY-mode TShark utility
The most powerful display filters in the industry
Rich VoIP analysis
Read/write many different capture file formats: tcpdump (libpcap), Catapult DCT2000, Cisco Secure IDS iplog, Microsoft Network Monitor, Network General Sniffer® (compressed and uncompressed), Sniffer® Pro, and NetXray®, Network Instruments Observer, Novell LANalyzer, RADCOM WAN/LAN Analyzer, Shomiti/Finisar Surveyor, Tektronix K12xx, Visual Networks Visual UpTime, WildPackets EtherPeek/TokenPeek/AiroPeek, and many others
Capture files compressed with gzip can be decompressed on the fly
Live data can be read from Ethernet, IEEE 802.11, PPP/HDLC, ATM, Bluetooth, USB, Token Ring, Frame Relay, FDDI, and others (depending on your platfrom)
Decryption support for many protocols, including IPsec, ISAKMP, Kerberos, SNMPv3, SSL/TLS, WEP, and WPA/WPA2
Coloring rules can be applied to the packet list for quick, intuitive analysis
Output can be exported to XML, PostScript®, CSV, or plain text.
work the OSI model from the bottom up
Physical (Do you have a network adapter/connection)
Link layer (arp, ethernet port blocked by network team (I've seen this where locked down environments see two MAC addresses coming from one workstation port and shut down the port)
Network layer (ipconfig, tracert, ping,)
Do you have a network address (DHCP, fixed)
Are you on a proper subnet/have routing between subnets
Is something in the middle blocking you
firewalls, routing tables
When in doubt, check to see if the windows firewall is messing with your communications. 8 times out of 10, it's at fault.
Using tracert is a good start to see how far along the chain you are getting.
For virtual machines it's usally a good idea to make sure you have the loopback adapter set correctly in the Host os.
Most frequently used tool is the ping. It can be used both to test your connection and the availability of a target
Second tool is the tracert if you want to see where the packets get lost.
For more advanced debugging I use the following tools: nmap, wireshark, etc.
Windows has a netstat utility which is pretty similar to the Unix netstat and can do a number of different things that might help you solve network issues.
Random example:
netstat -r displays routing information
netstat /? for usage information
Since you said you're using 2 virtual machines I would hazard a guess that both machines are setup in a NAT configuration (rather than a unique network device) -- In the NAT configuration, neither machine would (typically) be able to ping the other.
If you're familiar with the command line, you can try the "netstat" command.
You can also try "arp -a" to list all the IP/MAC addresses known to your PC.
The "tracert [ip address]" command will show you how many gateways/routers your packets jump through on their way to their destination. (This is probably not helpful if both machines are on the same network, though.)
And don't forget to check your Windows firewall settings.
Otherwise, if you want to get down and dirty, you can try the packet sniffer known as Wireshark: http://www.wireshark.org/ (aka. Ethereal)
Pull the network cable out
If you can get some communications to a device (eg a ping), but can't get your program to talk to a service on the computer. Then, try pulling the network cable out and see if the ping stops. This will verify you're communicating with the computer you really think you are.
On windows i user PortQueryUI : http://www.microsoft.com/en-us/download/details.aspx?id=24009
DNS activity: Portable DNS Cache and Firewall;
General network activity: Wireshark, Network Monitor;
Windows utilities: ping, netstat, nslookup.
You need to be use the process of elimination, for example if you can ping the ip address but not the hostname then there's DNS issues. If you can ping the system but not connect to a share etc.
DNS out of sync
If you're using a virtual machine and you perform a roll-back on it, then it could become out of sync with the DNS (Domain name server). Try to remove and re-add the machine to the domain, or if you've got access to the DNS machine, then get it to flush its cache.