I'm in somewhat of an odd situation here. I'm looking to send SMTP e-mails from a remote embedded system which is directly connected to an iridium modem into a local server. The current system sends files in chunks of data and I don't know exactly how this would work with e-mail. I was thinking of using mutt to send attachments (.wav or .jpeg files), but again I don't know if this works without direct internet access. If anyone has any idea if this is possible, please let me know.
Edit: I'm using RUDICS communication, not a SBD modem
Thanks
The Iridium Short Burst Data (SBD) service sends burst of less that 2Kb at a time and the revenue model for Iridium service might make sending audio and image data very expensive.
Nonetheless messages are converted by the Iridium network to be delivered in email format or over HTTP to a pre-configured address. The address to which data is sent is assigned to your Iridium service subscription, not stored or configurable by the sender. You can of course forward the received data to any desired destination.
You can get a direct Internet connection using an Iridium phone (https://www.iridium.com/services/details/iridium-direct-internet); but that is an expensive and bulky solution.
It's possible but somewhat complex. You would need to setup a PPP connection with the modem and then email would be able to flow across the serial line to the other server.
Related
this is my first question here and I realize this question might be open ended, but I'm looking for specific solutions, and any solution would be accepted.
I have GPS devices which send data packets to an IP on a port, both of which I can configure. I wish to use one of Google's, Amazon's or Microsoft's offering of cloud services. I am using python. Here is an implementation I found online :-
https://github.com/rdkls/gps-tracker-server
The data is coming as packets which are not over HTTP protocol. I have considered building a network listener over a socket on Google Compute Engine, but I'm not sure if it will be able to handle simultaneous requests from 1000 devices if such a situation ever arises. The Google Cloud IoT core offering seems to fit my need perfectly, but it is in private beta right now, which means I can't use it. I think I'll need a message queue service. But most of the offerings from these three companies requires messages over HTTP. Keep in mind that I can't change how the messages are sent from the GPS devices.
The messages sent are in this format -
https://drive.google.com/file/d/0B2EklrIn3KugS2NJYWZGWlVWeGdMbjM4WHQ2TUZmYWhIRmt3/view?usp=drive_web
Format:
data is sent in (byte sized) packets directly to the IP:Port over GPRS connections, one heartbeat packet every minute and GPS details every minute from each device. It also requires teh server to eply to the messagee for acknowledgement since it's not over TCP/IP.
So basically, which service and which architecture should I use keeping scalability, reliability and cost in mind?
I think for a 1000 devices, that would send such messages every minute, total would be 43M messages. I'm not sure but I'm looking for something that'll cost me about 1000$ that is 1$ per device per month.
I have seen many of the posts relating to sending email under linux but they do not address my particular need.
I want to implement code (C/C++) in my linux application that will send me back some kind of notification (in a stealthy way) under a certain program condition. All it needs to send me is less than 50 bytes of status data. The only thing I am guarenteed is that the box will be on a local network which will have access to the Internet via the usual gateway.
One possibility would be to send me a text to my wireless carrier like this:
mynumber#verizon_gateway.com. But that assumes that I have a mail client available on the linux box which is not a guarantee. If I programmed this at the socket layer directly using SMTP I would have to manage a TCP connection which is not what I prefer to do.
Any suggestions of what would be a possible way to send me a notification from my linux app?
Thanks,
-Andres
For email you could use something like SendGrid, specifically their WebAPI - this will allow you to send email with only a HTTP request.
For SMS you could use something like Nexmo, which will allow you to send an SMS with a HTTP request.
Note that you'll have to include your API credentials in the compiled code - a potental security issue (for your credentials).
Disclaimer: I do a bit of developer evangelism for Nexmo.
I understand many of the fine details of NAT hole punching, ICE, and SIP VOIP calls. I've answered quite a few questions on SO on these topics. Now I have a question.
I am trying to understand the need for the RE-INVITE message that is documented for SIP+ICE after the call is already established.
Assume a topology of VOIP devices that signal over SIP and using ICE (with STUN/TURN) for establishing media connectivity. After the ICE connectivity checks are performed, both endpoints should have ascertained the best address candidate pairings (IP,port) and should be ready to stream media in both directions.
But my experience with SIP and plenty of documentation suggests that after the callee sends a 200 OK message to indicate he's in the answered state, the caller is to expected send a RE-INVITE with an SDP containing the specific address candidate selected by the connectivity checks.
Some links that describe the RE-INVITE with ICE are here and here (step 8). Rosenberg's tutorial (page 30) discusses that the RE-INVITE "ensures that middleboxes have the correct media address". I'm not sure why that's important.
Upon receiving a RE-INVITE, is the callee expected to reconfigure his ICE stack to switch sockets or addresses based on the new SDP received? Or is the RE-INVITE just a protocol formality to formally acknowledge the call has been established? If the RE-INVITE step was skipped and both sides started streaming media, what could go wrong?
The reason why I ask is because I am exploring using ICE over a signaling service that is not SIP. I'm trying to figure out if the RE-INVITE needs to be emulated.
One example of middlebox, which may be interested in the result of the ICE negotiation is a bandwidth manager.
Imagine an enterprise deployment, with endpoints inside the corporate firewall and others roaming around on the Internet, or behind private home firewalls. The deployment also includes a publicly accessible TURN server. Then let's imagine an endpoint inside the corporate firewall making a call. If the destination happens to be reachable on the same network, the call will go host to host and the TURN server will not be used (i.e. bindings will be de-allocated). This is a local network, and no bandwidth limitation needs to be imposed. On the other hand, if the call goes out to a roaming endpoint, then the TURN server will get involved, and data will flow through the corporate firewall, through what probably is a limited bandwidth uplink. We can very well imagine some policy that would want to limit the call's bandwidth. One way of doing it, is for the bandwidth manager to remain in the signaling path (using SIP record-routes) and look into the SDP of any INVITE going through, re-writing bandwidth values depending on media addresses.
I believe the general intention was, that legacy equipment of that type, which is not ICE aware, should keep working in a mixed environment introducing ICE endpoints. To keep this backwards compatibility, ICE should only introduce new processing (STUN checks, etc), but from the point of view of non-ICE-aware elements, it should not remove any existing rules (re-INVITEs are still needed to change the destination of a media stream).
In Rosenberg's tutorial I believe the re-INVITE is sent because the sockets chosen by ICE are different from those in the media and connection (m/c-lines) lines of the original SDP AND in order for any network elements that are in between the two user agents to be informed of the actual sockets that will be used RTP a re-INVITE is sent with the ICE selected socket(s) in the media and connection lines of the SDP.
If the ICE selected sockets were the same as the ones in the original INVITE request's SDP m/c lines then there would be no need for the re-INVITE request. Or if you know there are no "middleboxes" that need to be informed of the changes to the RTP sockets then there would also be no need to send the re-INVITE.
It doesn't relate specifically to any programming language or technique, but still:
You know how you can use programs like Wireshark to read packets going through your computer (or router, more accurately)? These packets can contain secret information that must be encrypted somehow, like username and password for some systems. But even without this information, one can recreate these packets and obtain the same information, no? For example, I can send these packets from my computer, pretend that I've requested the service and obtain access that way to the given system. How is that prevented?
Also, a kind-of-related question: when a router receives a packet, how does it know to which computer to direct it to if multiple computers are connected to it in an LAN?
What you describe is called a replay-attack - to prevent this sort of attack the respective protocol needs to have some built-in features (like some unique ID per request and becomes invalid after being received the very first time and/or becomes invalid after a certain amount of time and/or some timestamp etc.).
I want to a Java ME application that transfers any SMS received to a PC using bluetooth. The PC can then direct the Java ME application via bluetooth to send a response SMS. Is there library available for this architecture or I have to design it myself?
Is this approach correct or a better one exists? I want to use bluetooth as then I will not have dependency on the cable.
You'll need to create this yourself, however you'll find that you can't do what you want with J2ME.
J2ME can't access any old SMS that the handset receives, only ones sent to a specific port upon which the MIDlet is listening. So to get all the other SMSes, create a bluetooth serial/dial-up connection to your handset in the way I've described in this answer.
Create a PC client which repeatedly issues AT+CGML commands (as described in the AT command set document linked to in the answer above), to see when an SMS has been received. Use AT+CGMR to read and parse the message text. Then use AT+CGMS to sent a response. This can all be done over bluetooth.
It's better to use the serial connection to send a response, because a MIDlet cannot usually be triggered to open based on incoming bluetooth data.
Hope this helps.
You may have already achieved your task, anyway for the reference I think it is much better if you try using Gammu . I'm using it for the same task (Send / receive SMS through PC ) with a simple bat file I have written, works like a charm.
Anyway you don't need any J2me program for this.
Wammu takes care of making the connection to phone and sending AT commands.