I would like to pass 1 or more telephone lines to a distant location threw a tcp/ip connection (lan) and export the line(s) threw some equipment to normal phones (no ip phones).
So there should be something like this:
line --- equipment --- wifi ---equipment---- normal phone.
I am working on networks but never worked on voip or anything like that.
So I would like to know what kind of equipment (except lan equipment) should I use in order to achieve it
Thank you.
You need an FXO box (for first equipment) and an FXS box for second one. There are lots of such devices as well as routers' modules. You need them both to support the same VoIP protocol, most probably SIP or H323.
Then you need to configure FXO to pass all incoming calls directly to FXS's ip address and FXS to pass all calls directly to FXO's.
Later you can add some IP pbx between them to implement more advanced call routing schemes.
Related
I want to send data(I think I can achieve it sending http requests) between two ESP's that are connected to the same LAN. I don't want to use one as an access point! I have one esp that is acting as a homekit device, and I want to send data(for example, sensor readings) to it from another esp. I've seen many tutorials where one device is acting as an access point, but that's not what I need. I also don't really need to access the esp data directly from my laptop, so I believe I don't need the html page. I would appreciate any help, code, or any existing tutorials, because I didn't find a single one.
Configuring one ESP as an AP is only done for convenience. You can configure both of them in STA (station) mode and they will connect to, e.g. your phone hotspot or your wifi router.
Connected to the same hotspot, they are on the same network, and they will be able to communicate with each other (unless the hotspot is configured to not allow this ... ). The tricky part will most likely be for the "client" to determine the IP address of the "server" in order to create the connection.
If you have admin access to the hotspot, you can cheat and hard code the IP addresses (assuming that the hotspot will assign the same IP address to the device the next time it sees it.)
It's also not difficult to use mdns (aka bonjour), which allows a network device to assign itself a local hostname. So you can name one ESP ("myserver") which allows the ESP running the client code to connect to "http://myserver.local"
I have a RS-485 device connected via twisted pair to another RS-485 device.
I'd like to bridge the distance via Ethernet, like so:
RS485 > Ethernet > RS485
Is this possible with two RS485 to Ethernet converters?
[RS485 device] to [RS485-Ethernet] via cable to [Ethernet-RS485] to RS485
The RS-485 communication is bi-directional. As in, the master sends and asks for information. I thought of getting two USR-RS232-304 devices, which I'd like to use for this. Would these work for this purpose? What puzzles me is, one seems to be a server, the other client. Will this still allow for bi-directional comms on the RS-485 side?
I did read the manual, and while it describes the general setup of IP config and transmission parameters, I am not sure (or could not deduct from it), whether bidirectional RS485 would work or not.
Any diagrams I have seen show only one of these converters, with the other end being a virtual comport. The devices I have talking to each other are not computers, where I could load a virtual COM port; hence, my query.
Maybe someone has done exactly what I am after and can share.
Looking at https://www.pusr.com/download/M0/USR-TCP232-304-User-Manual_V1.0.3.01.pdf, it should work. I'd suggest speaking to their support staff directly. (this was once (circa 1992) referred to as two "half bridges", setting to 255.255.255.255 would be a "dumb bridge")
I would like to write a software running in a networked device, i.e. PC. It can automatically detect the other network devices' types. For example, it can detect there is a PS3, a Wii, an IPad running in the same network. Any ideas? Thanks,
You have two problems: first, detecting that a device is connected to your network and at 192.168.1.x. Second, somehow detecting what that device is.
The first is easy-ish to accomplish: there's discovery protocols like UPnP and Bonjour. However, in a home networking scenario, the easiest and most reliable way to get a list of connected devices is probably to pull the DHCP reservations from your router. You might have to scrape data from the router's HTML-based management interface—hacky as that may be—but it would work. (If you're using .NET, consider the HTML Agility Pack to accomplish this.)
Once you have a list of IP addresses of connected devices, your next problem is to figure out what each device actually is. This will be more challenging. Some possibilities:
You may be able to use the MAC address to help detect the device's vendor. (Here's a list.)
If you're using UPnP, you can ask the device what it is.
Use IP fingerprinting to determine what the device is.
Couple thoughts. The broadcast IP address - 255.255.255.255 is where devices talk and say "here I am". Should be able to listen to this and find ip addresses and more. Second, if devices are assigned an IP address by a DHCP client (obviously) you can usually find a list on the dhcp device. Devices often have names, this is a higher level protocol, like windows SMB, that you may have to interface with in order to get that information.
im wondering if it's possible to create p2p chat application without server(so there is no need in external static ip.Is it true?)?
EddieC is right if the computers are located inside the same sub-network (LAN) or if the computers'ip is their interface to the Internet (WAN public ip). In that case, you can just use the ip's and ports directly.
However, usually, knowing the computers ip is not enough because the machines are located behind routers inside sub-networks. Thus, because the computers are hidden behind the routers, you will have to configure the routers to foward the packets to the right computers as function of the ports used.
Have a look at : http://wiki.vuze.com/w/Port_forwarding
If you do not want to use ip's because they are dynamic, you can configure urls with Dynamic DNS services.
Good luck
It is possible. But you must have someway for one computer to tell the other computer what their IP number is. You could email it to your friend or call them on the phone or post it on a message board.
If this program only has to work on a local network (LAN), there is something called broadcasting which might be of interest to you. It allows a packet to be sent out to every device on the network without having to know their IPs (then other instances of your program could reply with the IP of their machines so you could set up proper connections).
This won't work over the internet, though (imagine being able to broadcast to every computer connected to the internet!).
I'm trying to implement a system that works with faxes. We have a gatewary, phone to T.38 (fax over IP). I need a library that will let me do the other end, T.38 to TIFF image. I'm doing this on a mac, and we work with C, C++, php, java.
A program that will quietly turn T.38 into T.37 (fax over email) would work just as well.
Does anyone know of either of these?
A T.38 gateway is really just the modem section to take FAX analog "audio" data on the phone line and turns it a straight binary digital packet stream of lower level T.30 HDLC data. The T.38 standard does specify some level of application level decoding to extend the timers in certain FAX acknolwedgement handshakes....in effect the T.38 gateway buys some time at his end with the FAX machine at the other end of the phone call while stuff makes it through the IP network...especially if there is packet loss etc. However, all of that is going on between the T.38 gateway and the FAX machine....not towards the IP network.
So, if you really want to peer into the IP packet end of the T.38 gateway and actually want to get access to the FAX'ed document images and render that as TIFF, what you really are looking for is T.30 FAX Termination since T.30 specifies the format of the HDLC data and how to encode/decode that content. In effect, you have to implement the FAX machine's logic to capture the documents into TIFF in the same way that a real FAX machine would have captured the images and printed to paper.
ie: What you are really for is a T.30 implementation, not a T.38 implementation. Note that part of the the T.30 standard also references T.4 which describes how the the actual image data is compressed within the context of T.30.
Relative to going from T.38 to T.37, while I suppose that would be theoretically possible, understand that just like T.38, the T.37 standard assumes that one end of such a gateway is the analog domain. That is, the standard of T.37 specifies how to go from analog to an email message in the same way that T.38 goes from analog to real-time digital packet stream. In the context of the standards there is no "double hop" from T.38 to T.37 to get to your FAX images....so I think finding an existing implementation seems unlikely.
In the end, what you need is a T.30 FAX termination implementation since the T.38 gateway you are talking to is already doing the modem part for you. Alternatively, another way of looking at this is that you want a T.37 gateway instead of a T.38 gateway.
Asterisk the open source PBX uses the SpanDSP library to implement faxing. It looks like that library has modules to handle T.38 and the other protocols InSciTek Jeff mentioned.
Hylafax may work for you, if you're willing to use linux somewhere.
I use asterisk + iaxmodem + hylafax. Hylafax is designed to receive/send faxes. Received faxes are saved as tiffs or pdf's or sent to an arbitrary script of your own making for processing. Hylafax expects to use real modems. Iaxmodem simulates a real modem while really being an IAX2 (voip protocol like sip) connection to asterisk.
If you're really hardcore, you could look at extracting the 'conversion' part out of hylafax and turning it into a library for your own use on the mac. It is open source.
OPAL is a library that supports T.38 (Only up to 14400) (It can also use spandsp to deal with G711 audio containing fax tones). Commercial options also exist, mostly from Dialogic and Commetrex.