If a Windows machine acts like a router (gateway) for others, will Winsock LSP filters that are installed on it be able to capture/mangle traffic of those machines?
If no, which technologies are there for this?
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I am trying to connect robot controler CODESYS program with OPC Expert through OPC UA server and that's listening 4840 port and on OPC Expert I'm getting like opc.tcp://hp-nb:4840/uadiscovery. I also installed freeopcua in my machine and that's listening 4840 port as well and on OPC Expert it's like opc.tcp//0.0.0.0:4840. On OPC Expert I need to connect with CODESYS application. I can connect with CODESYS OPC server but I'm not able to connect my application from CODESYS controler. Is it happening because of two servers are listening on same port? if not then how can I resolve my issue? Attached an image of my issue enter image description here
Two programs or processes running on the same computer cannot listen on the same port.
It would be possible only if that computer had two network interface cards with two different IPs and you could choose through which interface each process connect, a thing that is not usually possible to do
UPDATE
CODESYS Soft PLC emulator, which is usually installed with CODESYS, also includes an OPC Server listening on port 4840, if you stop the Soft PLC right clicking the icon on the windows notification area probably it will close the listening port
In theory, two OPC UA servers could share the same port (on the same network interface) if they coordinate together. For opc.tcp, there is no standard way for them to do it. Therefore, two servers from the same vendor that are written in such special way could theoretically share the port. In reality, however, OPC UA servers using "opc.tcp" cannot share the same port, because they do not know how to coordinate the access and route the data.
For other protocols the situation is different. E.g. for OPC UA over HTTPS it is easier to have servers listening on the same port - mainly because the operating system already contains a piece that can listen on the port "for them", and route the requests based on the URL.
In your situation, however, it is not just that two server cannot share the same port. There is also a problem with the fact that one of the servers returns "0.0.0.0" as its IP address in the connection point description, which is invalid anyhow.
I have an android client which has to communicate through socket to a c# based pc server. The question is, if the pc server is behind a router which somwhow does not seem to support port forwarding through upnp, or even through configuration, it simply cant get connection.
These routers are some kind of free wifi zones prepared for free by some kind of companies, so I can't have any access to it's configs. The upnp or configuring my router both works fine, but I dont really know what to do about these routers.
It's common for a home router to only allow established connections by default. Even with a VPN tunnel or CHAP Callback, you would still need configuration on both ends imho.
I know how to listen on a dedicated port using nsISocketTransportService in Add-on sdk. But, is it possible to use UNIX socket in Add-on SDK to communicate with oher applications.
It seems you can't: https://support.mozilla.org/en-US/kb/permission-request-messages-firefox-extensions)
This would make sense, since:
UNIX sockets are a special file on *nix
they are not available across platforms
this would be a huge security issue.
If you need to communicate with other software on the computer you can probably safely use regular network sockets, websockets, etc...
I have two servers, written in Java, that communicate through sockets and TCP. The servers are both on the same Linux machine. If the servers were on different machines then data would have to go through network adapters and network cables, but since the servers are on the same machine how does the OS actually move data efficiently form one server to the other.
Generally, the messages will be sent over the loopback interface:
In TCP/IP a loopback device is a virtual network interface implemented in software only and not connected to any hardware, but which is fully integrated into the computer system's internal network infrastructure. Any traffic that a computer program sends to the loopback interface is immediately received on the same interface.
However, you can manage to configure your situation so that, for example, the server is referred to via an external IP address so that messages actually go out over the network before being routed back to the same machine.
If two programs are using TCP/IP to communicate on the same machine, they are probably connected through the loopback interface
I am looking for MQ systems (rabbitmq , activemq) for our programs. Almost all MQ run on ports. I was wondering if there are any MQ systems running on smtp or email services.
Basically I am trying to avoid the hassle of setting up a new software and opening up ports in different firewalls (its a hassle).
RabbitMQ is designed from the ground up to interoperate with other messaging systems: it is the leading implementation of AMQP, the open standard for business messaging, and, through adapters, supports XMPP, SMTP, STOMP and HTTP for lightweight web messaging.
supports SMTP? from: http://www.rabbitmq.com/