I'm a beginner to ethernet programming, I want to access the ethernet port and send/recieve packets to/from it. I thought of using the CIM_EthernetPort class, but don't know how to do it. please help. I have to write a program to send data to an embedded system.
I don't think you quite understand what sockets are.
What protocol does your embedded device use? If it's TCP or UDP (or even a raw link protocol) it's pretty much using a socket by definition.
The only reason you might need to talk to an ethernet adapter without using sockets is if you want to write something like a wire level monitor or packet sniffer.
ps -------------------------------------------------------------
Sockets are just an abstraction of a network connection, since a UDP connection has an endpoint and a port it's a bit philosophical wether you are using sockets if you talk directly to the network card hardware.
You don't specify a baud rate as such on ethernet, the card hw will negotiate a speed.
There is very little overhead in sending data by UDP using sockets and it's usually a very efficent way of receiving data. Do you have an RTOS on the embedded device or were you trying to talk to the network adaptor directly with some sort of polling?
pps ------------------------------------------------------------------
If it is at all possible to use UDP on the embedded device - DO SO.
If you start with, I just need to send a few numbers, you ultimately end up re-inventing and re-solving all the things UDP was invented to do.
By using standard protocols you also get tools to let you test each end of the connection (there are UDP equivalents of hyperterm for free).
Also there is no need for multiple devices now, but there may be in the future. I argued for using UDP on a previous product I worked on - where the designers were thinking of ethernet as just a faster serial link. Being able to network many units of this product together has created a huge new market.
Related
First allow me to say that I don't have any experience developing drivers for OSX, nor drivers for Windows. So, there are a lot of things that I don't understand about how drivers work; I'm sure it'll be evident in my question.
I have a modem that is able to open and close TCP/UDP sockets using AT commands. I would like to create some kind of program (kernel extension? driver?) that implements a network driver, converting the network interface calls into AT command serial messages.
That's the basic jist of it. I'm essentially asking if anybody can point me in the right direction / give me a high level overview of how they would approach it and what Apple guides to focus on.
The XNU networking stack -- like most network stacks -- expects network devices to send and receive IP packets directly. It isn't tooled to work with network devices that handle part of the network stack (like TCP or UDP) internally -- it won't be possible to implement a network driver which uses this device.
You might have more luck exposing this device as a SOCKS proxy. You will need to write a userspace daemon which listens on a TCP port on localhost (on the computer) and relays traffic to the serial device; once that's done, you can set the computer to use that device as a SOCKS proxy in the Networking control panel.
(As an aside: most devices that implement this type of interface have a very low limit on the number of open sockets -- often fewer than 10. They're unlikely to be able to handle the network load generated by a desktop OS.)
Im new to socket programing . I wanted to send few data from Kernel to userspace. I wanted know socket of which family and protocol is suitable to create?
UDP,
TCP,
RAW,
NETLINK,
It will be better if anyone explains usecase of socket types.
Thanks in advance
Check the following socket API
int socket(int domain, int type, int protocol);
1)Netlink sockets are used for communicating between Userspace and the kernel space. Check the following link for example.
2)TCP(of type SOCK_STREAM) and UDP(SOCK_DGRAM) are used mostly for communicating over network. These sockets are of the domain AF_INET. TCP is used for file downloading like application, where delivey and order is guaranteed. UDP is used in cases where latency is important, than delivery or retransmission. Like in the case of Live Video stream. Even a frame of video is skipped, it still should not go for retransmission and slow down the 'LIVE' effect.
3)Then there is usage of sockets for IPC(Inter process Communication). In that case the domain is AF_UNIX and the type used can be SOCK_SEQPACKET(similar to TCP)
I have a created hardware communicating application using RS232 protocol in MFC. But as there is problem regarding voltage signal strength, i would like to shift from RS232 to TCP/IP.
Can anyone help me on this topic...?
The solution is to extend the microcontroller board with a serial device server.
Known brands are Lantronix or Moxa, but there are many other options and manufacturers. For an "embedded" solution that is integrated on your board, the "Lantronix XPort" is a typical product.
http://www.lantronix.com/device-networking/embedded-device-servers/xport.html
(I'm not affiliated with the Lantronix company.)
The Serial Device Server will connect to your RS232 on one end, and on its TCP/Ethernet side it offers usually a TCP server. It is usually configurable via network, through a built-in web interface, much like an Internet router.
Your PC application then needs to be changed as follows: Instead of opening a Windows COM port, you need to make a TCP client connection to that server, on a preconfigured TCP port. (Lantronix has 10001 as the default TCP port for this.)
But there is also special Windows driver software that lets you talk to your Serial Device Server / your microcontroller through a "virtual COM port". This is sometimes the best solution for legacy PC applications, where you cannot change the original code and have to use a Windows COM port. For a MFC application this might be a good choice.
I discovered almost accidentally that my machine was sending and receiving UDP packets to a machine in Poland. Not that I have any problem with Poland, I just don't know why my laptop has the need to communicate with a server there. Reverse DNS shows just the ISP providing the address to some end user. Using Wireshark, I can monitor the messages, which were indecipherable as they were probably encrypted. All packets sent from my machine had the same source port, so clearly the application that sent them opened this UDP socket to use it. I am searching for ways to:
1) enumerate all current sockets open in the system, including the process that created it and, for both TCP and UDP, what ports and addresses they are current bound to.
2) because applications can open these sockets, use them, and close them right away, I would love to find (or perhaps even write) a program that once started would somehow get notification each time a socket gets created, or really more importantly when bound to a source and/or destination address and port. For UDP, I would love to also be able to monitor/keep track of the destination IP addresses and ports that socket has sent messages to.
I don't want to monitor the traffic itself, I have Wireshark if I want to view the traffic. I want to be able to then cross reference to discover what application is generating the packets. I want to know if it is from a process I trust, or if it is something I need to investigate further.
Does anybody know of any applications (for the Windows platform) that can do this? If not, any ideas about a .NET or Windows API that provides this capability, should I want to write it myself?
Edit:
After further research - looks like the APIs to use are GetExtendedUdpTable and GetExtendedTcpTable, CodeProject.com has some samples wrapping these in .NET (see http://www.codeproject.com/Articles/14423/Getting-the-active-TCP-UDP-connections-using-the-G). So a combination of this API and some sniffer code would be needed to monitor and keep track of what hosts at what ports using what protocol any particular application on your machine is talking to. If I ever get some free time, I'll consider creating this, if you know of an app that does all this, please let me know.
Try SysInternals TCPView. Despite its name, it handles UDP as well.
netstat -b to enumerate all ports along with the process names.
You can try using SysInternals' Process MOnitor (ProcMon.exe or ProcMon64.exe).
It allows for filtering of Processes by "UDP Send" Operation - and provides detailed UDP Connection data, including source and destination addresses(IP) and ports etc.
I wonder if the UNIX domain socket connections with postgresql are faster then tcp connections from localhost in high concurrency rate and if it does, by how much?
Postgres core developer Bruce Momjian has blogged about this topic. Momjian states, "Unix-domain socket communication is measurably faster." He measured query network performance showing that the local domain socket was 33% faster than using the TCP/IP stack.
UNIX domain sockets should offer better performance than TCP sockets over loopback interface (less copying of data, fewer context switches), but I don't know whether the performance increase can be demonstrated with PostgreSQL.
I found a small comparison on the FreeBSD mailinglist: http://lists.freebsd.org/pipermail/freebsd-performance/2005-February/001143.html.
I believe that UNIX domain sockets in theory give better throughput than TCP sockets on the loopback interface, but in practice the difference is probably negligible.
Data carried over UNIX domain sockets don't have to go up and down through the IP stack layers.
re: Alexander's answer. AFAIK you shouldn't get any more than one context switch or data copy in each direction (i.e. for each read() or write()), hence why I believe the difference will be negligble. The IP stack doesn't need to copy the packet as it moves between layers, but it does have to manipulate internal data structures to add and remove higher-layer packet headers.
afaik, unix domain socket (UDS) work like system pipes and it send ONLY data, not send checksum and other additional info, not use three-way handshake as TCP sockets...
ps: maybe UDS will be more faster
TCP sockets on localhost are usually implemented using UNIX domain sockets, so the answer on most systems is neglijable to none. However, this is not standard in any way -- it is just how usually it is done, therefore you should not depend on this.