does every app running on the 21.co platform need its own unique port?
I am running several different applications on the 21.co bitcoin platform and I notice that each software developer assigns their own port numbers. Often the default is 5000. Can I have several apps all sharing the same port?
No. Per 21 support on the 21co.slack.com channel, every unique app requires a unique port number. There are at present no facilities for managing port assignment.
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My company uses a third party product to manage subscriptions. The subscription database is set up on a server we control and we have four machines set up with the client application. Those four machines are the server machine and three others.
We are limited to four licenses, and the way the client application is installed is with different modules. The same machine is only supposed to consume on license, regardless of how many modules are open. It does this by supposedly pulling the net_address from the master..sysprocesses table. In theory, my company has enough licenses for all four machines to connect to the database, but one of my users is saying that they receive a notice that there are no further licenses available.
When I check the database, I notice that of the four machines, only one of the net_address's matches the hardware address (MAC) of my four machines that have the client application installed. I have confirmed no breaches, but I am not understanding where these net_address entries are coming from. The support team for the application insists that they should match the physical hardware(MAC) address, and with one of the client machines doing so that may be true, but I am not sure where these other addresses are coming from.
All the devices are behind the same router, so the MAC of the router shouldn't be coming in to play (and doesn't match any of the unknown entries), and none of the machines are behind any other L3 switch. They are connected via ethernet, and I am not seeing any installed applications that would cause MAC spoofing. The server machine itself is one of the devices with a net_address that doesn't match the MAC of the active NIC, and tracert only shows one hop.
What would be some other reasons that net_address wouldn't match the MAC of the connected client machine?
I want to create a desktop application using vb.net and sql-server. I have two computers and I have my sql-server installed in one of the machines (server) in this case. I want to access the database from that (server) using another computer but the challenge is, I don't have any internet connection. All I have is a network cable to connect these two computers the one serving as a server and the client machine. Is this possible to access my database or can only be achieved over an internet connection? If possible how can I go about it?
Yes this is possible, if you only need to connect two computers, you'll not even need a switch or hub. You only need to assign both computers a private IP address in the same address space, such as 10.0.0.2 and 10.0.0.3 for computer A and B.
However, it might still be reasonable to use a switch for your purpose, as you might need to expand your network and/or connect to the internet in future cases, but in your particular case, it is not mandatory.
Well..I have found some third party application regarding sending data from com port to IP. but I have not found any basic tutorial regarding them. so can anyone help me with this? I have a GPS device which I will connect to my laptop through usb to serial adapter.Now I need to send that data from a laptop to another laptop on same network. Can I use putty to view that data in another laptop(receiver)? Is virtual serial port driver meant for this kind of application?
If you do not want to write your own tool for it, you can simply use ncat and set up a daemon that reads piped data from one process and broadcasts it to all connected clients.
If you want something that reads the data from the serial port and then transmits it to clients, you'll need to write a server application that accepts connections and sends data around, but there's entire books on this. It should be easy to do for your purposes as written here, but it depends on the amount of control you need.
Alternatively you can use a virtual serial port application as you had mentioned, which might be the easiest route. The two devices will need to be on the same network unless the application supports TCP based virtualization instead of the common Ethernet based implementation.
This Python script works very well as a free "device server". Just enter the serial port configuration and the IP address and port information.
https://github.com/jaredly/pydbgp/blob/master/symbian/serial_tcp_redirect.py
This can work on both Windows and Linux.
You need pyserial.
You can always try using stand alone hardware such as the SENA LS100 device server.
we are currently considering whether ns3 satisfying our requirements, we're looking for a convenient tool to run in distributed devices in the real network (every kind of possible connections) and capture the network performance data (like a sniffer). I realize that the primary purpose of ns3 is to simulate network topology in a single machine, but its emu module sounds promising and the flow monitor can save our effort on data capture.
In the following link
http://www.nsnam.org/wiki/HOWTO_make_ns-3_interact_with_the_real_world
it is declared that NS-3 EMU can be applied to inject simulated nodes interacting with real live network, and 3 kinds of testbed are given. However the first solution, virtual machine vmware testbed is still woking within LAN -- in promiscuous mode the virtual machines network card are listening to all LAN broadcasts so that the emu-udp-echo server and client can find each other.
My question is, is it possible that the emu-udp-echo server/client running in different, physical systems from different positions in wide network?
e.g. in different cities or from different network providers, given ip address of the hardware where the other ns-3 node is running? if it is possible, how can i specify the "real" ip address and port for the node, instead of assign a virtual ipv4 address?
Thanks a lot.
Yes, while the documentation describes how to perform this using virtual machines, this can be done in general on real hardware. Since that HOWTO was written, there has been additional work on providing helpers for running this type of experiment, including running on PlanetLab testbed machines. This documentation describes the generalized file descriptor NetDevice, added to the ns-3.17 release: http://www.nsnam.org/docs/release/3.19/models/html/fd-net-device.html. A similar example to the one described in that HOWTO is found in the file fd-emu-udp-echo.cc.
When using emulation mode on real networks, configuration of the MAC addresses and IP addresses must be done carefully. First, the device must be able to be put into promiscuous mode. Second, the MAC address needs to be different than the hardware address of the NIC. If you intend to be riding on top of an active NIC with existing IP address (in use for other Internet traffic), you'll need to have another IP address for ns-3 that is within the right link subnet. If instead you want to dedicate the NIC to ns-3 use, then do not assign the IP address to the host NIC and just assign it to the ns-3 configuration.
The PlanetLab example also shows another configuration that uses Tap devices to send data to/from PlanetLab testbed nodes. Some of this configuration is specific to how PlanetLab works, but the use of Tap device bridged to an ns-3 device may also facilitate emulation.
version: erlang R13B
Hi all,
how can I increase the amount of ssl ports/handles that my network server is able to create on Windows?
On linux I was able to successful create about 1000 connections using:
-env ERL_MAX_PORTS 80000 -P 268435456
and changing the maximum open fd's using ulimit.
On windows apparently there is no effect using the same configuration, and sadly the number of open connections are VERY small (about 30, and it opens 6 handles for each one). I've noticed that the shell starts two other children processes, inet_gethost.exe and ssl_esock.exe. If these are the ones that I have to increase the port count, how do I do that?
Thanks,
According to this, in Windows NT
the maximum number of sockets
supported by a particular Windows
Sockets supplier is
implementation-specific. An
application should make no assumptions
about the availability of a certain
number of sockets.
According to this, you should redefine the value of FD_SETSIZE.
It also suggests to have a look to WSADATA.iMaxSockets.