My problem is i have only one machine which have one ip(192.168.1.2) and one port(502), but we have to get informations from more than one services. Is that possible to use multiple tcpclients to connect to different servers at the same time? or other solutions please?? by the way, i encounter this problem when read different Modbus server to get device realtime information.
It seems we can solve the problem by using SetSocketOption to reuse address and port.
var masterClient = new TcpClient(AddressFamily.InterNetwork);
masterClient.Client.SetSocketOption(
SocketOptionLevel.Socket,
SocketOptionName.ReuseAddress,
true);
masterClient.Connect(address.ToString(), 502);
Related
I have two services that are deployed in the two different VMs. I want to call one service from other to get some data via APIs. That should need to have an ultra-low latency call.
For that how can I used the Chronicle-Network (https://github.com/OpenHFT/Chronicle-Network)?
Or Any other solution?
I would suggest using Chronicle-Queue for passing messages from one service to another and back again. This is much lower latency than using TCP and easier to work with, provided the two VMs are on the same machine. You also get a record of every message making testing/debugging easier.
https://github.com/OpenHFT/Chronicle-Queue#high-level-interface-for-readingwriting
If you have two different machines I suggest either moving one VMs or using a low latency network card like Solarflare or Mellanox.
If you have a network call between VMs, try to use Chronicle Network.
Another option is Aeron UDP unicast connection - https://github.com/real-logic/aeron
Is it possible to connect to a Air app running on another machine via socket(assuming we know ip) or some other mechanism(which doesnt use Cirrus/stratus)? If it is can someone please help me on how?
Let me rephrase question, I dont want to connect to a server over socket. I would like to know if it is possible to connect from one AIR app on machine A to connect to another AIR app on machine B via sockets without cirrus. I'm not asking for someone else to do my work, I couldnt find any documentation or possibility of the above thing. My conclusion now is that it is not possible, but I would just like it to be verified by other people(experts).
Absolutely, as3 supports sockets. http://www.ultrashock.com/forum/viewthread/81676/
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/net/Socket.html?filter_flash=cs5&filter_flashplayer=10.2&filter_air=2.6
There are two ways to do it. One AIR app can act as a server by creating a ServerSocket object while the other app connects to this with the Socket class. The other way is to use the DatagramSocket class.
In both cases, the trick is that because of network access translation, the IP address to use is not always easily discoverable unless at least one of the computers has a static IP. If both computers are on the same network subnet you can look up the IP address needed to reach one computer from the other manually. Otherwise, the IP one computer must use to reach the other won't be the same IP that the computer sees for itself. This matchmaking is the service that stratus/cirrus provides.
See http://www.brynosaurus.com/pub/net/p2pnat/ for a description of the problem.
I wrote an server application in erlang and a client in C#. They communicate through 3 TCP ports. Port numbers are hardcoded. Now I'd like to do this dynamically. This is my first time doing network programming, so please pardon my inability to use proper terminology :-D
What I would like to do is make a supervisor which would accept a TCP connection from a client on a previously known port (say, 10000, or whatever), then find 3 free ports, start a server application on those 3 ports and tell the client those port numbers so client can connect to the server.
My particular problem is: how do I find 3 ports which are not in use? (clarification: which module:fun() to use to find a free port?)
My general problem is: I'm sure this kind of stuff (one server allocating ports and redirecting clients) is quite common network programming problem and there should be a bunch of (erlang-specific or general) resources about this, but I just don't have the terminology to google it out.
According to the Erlang documentation here, if the Port argument to the gen_tcp:listen/2 function is 0, then the OS will assign any available port to the socket. The latter can then be retreived using inet:port/1 .
You can therefore do something like this :
{ok, Listen} = gen_tcp:listen(0, [Options]),
Port = inet:port(Listen).
just in case you didn't know that - you dont have to allocate new ports for each client, it's perfectly fine to have all clients to connect to same ports
UPDATE:
if there is a reason to allocate new ports for incoming clients then it's far beyond your first "introduction to network programming" program.
separate ports could mean you want to completely isolate environments of different groups of clients. it's comparable to providing completely different IP addresses to connect to. if you want to write a simple ping-pong program - you don't need it. and i honestly believe you will never need to use such solution in your whole life - that's how incredibly rarely it is.
regarding cpu/ports overhead - allocating ports and starting a server that listens to that port is already far bigger overhead than accepting clients on same port.
You need to avoid commonly known ports, ftp, http, smtp etc, But I don't think there is any master list of which ports other software uses that you should avoid. I think your best bet is to come up with a range of ports you want to use. Check at runtime if anybody else answers ( is using the ports ) on the numbers you choose dynamically, if not issue it to the client.
My app needs to access two network cards. One to receive data (eth0) and another to send data (3G modem).
Normally, the kernel force the app to work with only one card at a time.
Is there any thing that I can do to make it run?
Thank you.
The kernel does no such thing.
The kernel will route your traffic to the most appropriate end destination based upon the routing information and networks each card is assigned. However, if you are using TCP, your bidirectional communication will use only one route as there is only one address associated with that connection.
If you are trying to implement an multi-homing send/receive system, this is not supported in normal TCP - you will need to use a different protocol, likely implemented in the kernel.
The kernel is not forcing you to use a single interface. It just chooses a default interface if you don't specify otherwise. You can specify a specific interface by specifying it's IP address in the bind() command. To get a list of the available interfaces and their names, use the ioctl(SIOCGIFCONF) function.
Here's an example: http://techpulp.com/2008/10/get-list-of-interfaces-using-siocgifconf-ioctl/
You can make two different UDP sockets bind to separate NICs with the bind(2) and send on one and listen on the other.
I have an application that is being built using Qt. It will be running on machines that will have two (or more) network cards. I need the ability for my application to select which ethernet interfaces for a TCP connection. Before anyone suggests it I cannot guarenteed that routing tables will be setup correctly. I know how to do this using the windows socket classes but have been unable to find anything about it for Qt. Any help would be greatly appreciated!
Are you referring to an outbound connection or an inbound connection?
If you're referring to an inbound connection, all you need to do is specify a QHostAddress to the QTcpServer::listen call.
If you're talking about an outbound connection, you can call QAbstractSocket::setLocalAddress to force the local address to something specific.
Cheers,
If you are using Qt 4.2 or later, you can use QNetworkInterface to get a list of network interfaces in the computer and then create some sort of network interface selection.