I wonder if I can use TCP connection protocol or something similar to it to convert IP to Address name
ex:
192.168.1.10:8080 //convert this ip to for example >>
my.localpc.com // or thomething looks like this
so Where I can start from
I like if suggestions related to these lang.s (C# , Python , C++ , MATLAB)
here is the story
"..
I was building an ROV for a competition and I used TCP IP to transfer date from PC to Raspberry PI but the IP always changes whatever I use fixed IP sometimes I have to change the TCP port then I'll change the port on the client program as well , so I asked myself if there is a way to call the ROV like http\myROV.com .. instead of 192.168.1.5:8080 .. which may change on several situations "
Thank you
Anything that can access normal sockets functions directly should be able to use gethostbyaddr or gethostinfo.
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'm using a PXI 8109 running Pharlap OS.
I'm trying to use the second ethernet interface of my PXI to send UDP and TCP packets.
Here the configuration of my two ethernet interfaces:
eth0 (primary):
IP : 10.0.0.3
subnet mask : 255.0.0.0
eth1 :
IP : 192.168.10.9
subnet mask : 255.255.255.0
For UDP, I have no problems, packets are sent to the second interface as I want. I think it work because there is a "net address" input on the "UDP Open" VI so the system can choose the right interface.
For TCP, I use the "TCP Open connection" VI but there is no this kind of input. And it is not working : I assume the system is trying to use the primary interface but it can't route packets...
For information, my two networks are physically independant.
Can you help me finding out what's going on ? Is it possible to use TCP on the second ethernet interface ?
TCP open is meant to open a connection to another computer, if you feed a valid (in one of the two subnets) TCP address it should open a connection on that specific interface.
I assume you need to use the TCP listener function and according to this KB article, you can specify on which address you want to listen. So yes, you should be able to use a specific ethernet interface.
disclaimer: I am not sure if all this info is valid on Pharlap as well.
Basically, the decision which NIC to use is up to the OS and I believe that normally it would choose based on the subnet of the address you're trying to connect to and those of the NICs - I don't know what the IP address is (maybe it's in the subnet of the wrong card?), but the subnets of the NICs certainly appear to be different from each other (10.0.0.0 and 192...).
On Windows, I believe you can set the routing tables to have some more control of this (although I don't know if you would be able to force something to go through the "wrong" NIC), but I have no idea how much control you would have over this on Phar Lap. I would suggest some searching. Here are a couple of relevant links:
http://forums.ni.com/t5/LabVIEW/RT-How-do-I-use-two-independent-Ethernet-ports/td-p/721269
http://forums.ni.com/t5/LabVIEW/Communicating-through-two-ethernet-ports-on-the-same-computer/m-p/1509450#M565374
I finally solved my problem. This was not related to the TCP connection ...
I was using a property node "Value (signaling)" to trigger the TCP connection and it seems that this is not supported on RT Targets.
This is why it was working on localhost.
Thanks for the help anyway ;)
I am programming a server and client program to communicate between a windows PC using the Boost libraries and a Linux ARM beagleboard using the asio stand alone libraries. I have for a while had successful UDP communication between the two devices but now I want to recover the port from the endpoint the server discovers when the client connects. The way the client connects is via query:
udp::resolver resolver(io_service);
udp::resolver::query query_tx(udp::v4(), hostIP, "43210");
udp::endpoint receiver_endpoint_tx = *resolver.resolve(query_tx);
where host IP is a string and this works fine. Upon debugging though I notice that when i check the value returned by:
receiver_endpoint_tx.port()
This returns 51880. Now don't jump the guns and yell out network byte order and host byte order. I AM AWARE. The strange part is that this number 51880 sometimes is a different number and when i check what the server has stored in its endpoint it is a completely different number: 21743. Now I know I must be doing something wrong with the byte orders but i tried:
//unsigned long port_long = boost::asio::detail::socket_ops::host_to_network_long(receiver_endpoint_tx.port());
//unsigned long port_short = boost::asio::detail::socket_ops::host_to_network_short(receiver_endpoint_tx.port());
And they do not give me back my original port: 43210. Neither does network to host. So what am i missing and how can I on both ends recover my 43210 port? Obviously it must be there somewhere because they are successfully communicating.
Thanks in advance, sorry if noob mistake :)
Fistly, UDP is connectionless, there is no connection.
I'm not sure if I understand you correctly, but it sound too me like you want to bind to specific port numbers. If you want the client to send a packet from port x to port y on the server, and the server should respond from port y to port x, then you need to bind the sockets to the desired ports. Alternatively you can use the constructor to bind. Not doing so will result in the OS using ephemeral ports.
Further, to get the remote endpoint that a packet was received from the async_receive_from takes the sender_endpoint reference parameter. When the read handler is called, you can retrieve host and port from it.
i was learning socket programming in unix using c/c++.
I am confused with one function call bind(params..).
Actually it takes the adreess structure "sockaddr_in" and we can create the structure in the following way
sockaddr_in.*** = somthing..
sockaddr_in..s_addr htonl(INADDR_ANY)
**Passing INADDR_ANY will alow to bind all local addresses**
My question is , why do we need to use "INADDR_ANY" ?
In my knowledge every machine can has only one unique IP Address. In this way there is only one address associated with the machien. Thye bind call should directly bind the socket to the single available address.
Please explain what are the different scenarios and why is it so?
A machine usually has an IP address for each connected network interface plus 127.0.0.1 for localhost (loopback). For example, a laptop might be connected to a wireless network as 10.0.1.25 and also to a wired network as 10.0.2.4. Servers often have an interface to an internal network as well as a public network.
It's possible for a machine to have more than one IP address, either because it has multiple network cards or through software. INADDR_ANY lets you bind a socket to all of the machine's IP addresses.
Not true. Most machines are Multi-Homed, that means, they have more than one IP address.
For example, the network address and 127.0.0.1.
Suppose two web browsers are running on the same computer and are accessing the same website (in other words, accessing the same IP address on the same port).
How does the operating system recognize which packets are from/for which program?
Does each program have a unique id field in the TCP header? If so, what is the field called?
The two programs are not actually accessing the "same port." For purposes of TCP, a connection is defined by the tuple (src_ip,src_port,dst_ip,dst_port).
The source port is usually ephemeral, which means it is randomly assigned by the OS. In other words:
Program A will have:
(my_ip, 10000, your_ip, 80)
Program B will have:
(my_ip, 10001, your_ip, 80)
Thus, the OS can see those are different "connections" and can push the packets to the correct socket objects.
the source port number will be different even if the destination port number is the same. the kernel will associate the source port number with the process.
When the client opens a connection to destination port 80, it uses an arbitrary unused source port on the local machine, say 17824. The web server then responds to that client by sending packets to destination port 17824.
A second client will use a second unused port number, say 17825, and so the two sockets' packets will not be mixed up since they'll use different port numbers on the client machine.
Christopher's answer is partially correct.
Programs A and B actually have a handle to a socket descriptor stored in the underlying OS's socket implementation. Packets are delivered to this underlying socket, and then any process which has a handle to that socket resource can read or write it.
For example, say you are writing a simple server on a Unix like OS such as Linux or Mac OSX.
Your server accepts a connection, at which point a connection consisting of
( src IP, src Port, dest IP, dest Port )
comes in to existence in the underlying OS socket layer. You then fork a process to handle the connection - at this point you now have two processes with handles to the socket both of which can read / write it.
Typically ( always ) the original server will close it's handle to the socket and let the forked process handle it. There are many reasons for this, but the one that is not always obvious to people is that when the child process finishes it's work and closes the socket the socket will stay open and connected if the parent process still has an open handle to it.
By port number.
IP address is used to identify computer, and port is used to identify process(application) within the computer. When a port is used by one process, other processes can't use it any more. So if any packet is sent to that port, only the owner of that port can handle that packet.
Connections are identified by a pair of endpoints.
– Endpoint means (ip, port)
Os assigns random number as src port number so, when packet travels to the receiving side, it is treated as different process's msg, since src port numbers are different.