I develop a network program that is used to transfer files , it works . But I just know it can works , and I don't know how to monitor and evaluate it . So I want to know what aspects a network program usually need to consider and monitor and how to monitor .
First make sure which protocol you have been used to send files (either TCP or UDP).
1.If you are using TCP at transport layer ,at the receiving end you can use TCPDUMP
packet analyzer to analyze all packets receiving on TCP port and its content.
2.If you want to analyze packets irrespective of protocols used at different layers, you can use wireshark packet analyzer to analyze all packets received on different networks like ethernet,PPP, loop back ,frame relay. you can use IP address of sender host as a reference to extract packets ( you need some reference to extract packets because wire shark will return all the packets received on the NIC interface). Once you extract the packets received from your sender host, you can analyze the packet payload to check whether files content has been received properly or not.
3.you can redirect data ( payload) of all received packets into some file. Once your program is done with receiving packets, you can check with that file to check data has been properly received or not. ( you can use this method only to test your client/server programs within a system)
Related
I am an embedded software developer who has any experience with TCPIP on connected devices. Also, I am not a software protocol expert, so I am a bit confusing about TCPIP protocol stack + responsiblities of its various phy layers.
First of all, I have experiences with such protocols like UART, SPI, CAN, USB... As you know, the phy layer directly affects you while selecting the protocol you used at the software level. For example, if you use usb and you build a software protocol on it, you do not occasionally deal with some details like checking corrupted frame in your sofware protocol, because phy layer of it guarantees this operation. CAN also has some CAN Controller facilities like crc and bit stuffing so, it is really reliable. But the situation is not the same for simple peripherals like UART/USART. Let's say you are using a bluetooth module to upgrade your firmware, you need to be aware of almost everything that can occur while communicating like delays, corrupted frames, payload validating etc.
Briefly, i am trying to understand the exact role of newtork interfaces come included in MCUs, that are interfaced with RJ45 phy sockets directly. In another words, imagine that I wrote a server application on my pc. Also i configured and ran an application in my development board which has an RJ45 socket and it runs as a client. Also imagine they established a connection over TCP. So, what will be the situation at the client side, when i send a 32 bytes of data to the socket from the server side? What will I see at the lowest level of MCU that is an RxCompleteInterrupt()? Are the data I sent and some other stuffs appended to the TCP packet guaranteed to be delivered by the eth controller in the MCU and ethernet controller of my PC? OR am i responsible (or the stack i used) check all the things necessary to validate whether the frame is valid or not?
I tried to be as clear as it would be. Please if you have experience, then try to write clean comments. I am not a TCPIP expert, maybe I used some wrong terminology, please focus the main concept of the question.
Thanks folks.
If you don't have any prior experience with the TCP/IP protocol suite, I would strongly suggest you to have a look at this IBM Redbook, more specifically at chapters 2, 3 and 4.
This being said:
So, what will be the situation at the client side, when i send a 32
bytes of data to the socket from the server side? What will I see at
the lowest level of MCU that is an RxCompleteInterrupt()?
You should have received an Ethernet frame in your buffer. This Ethernet frame should contain an IP packet. This IP packet should contain a TCP packet, which payload should consist in your 32 bytes of data. But there will be several exchanges between the client and the server prior to your data to be received, because of TCP being a connection-oriented protocol, i.e. several Ethernet frames will be sent/received.
Are the data I sent and some other stuffs appended to the TCP packet
guaranteed to be delivered by the eth controller in the MCU and
ethernet controller of my PC? OR am i responsible (or the stack i
used) check all the things necessary to validate whether the frame
is valid or not?
The TCP packet will ultimately be delivered, but there there are not warranties that your Ethernet frames and IP packets will be delivered, and will arrive in the right order. This is precisely the job of TCP, as a connection-oriented protocol, than to do what is needed so that the data you are sending as a TCP payload will ultimately be delivered. Your MCU hardware should be the one responsible for validating the Ethernet frames, but the TCP/IP stack running on the MCU is responsible for validating IP and TCP packets and the proper delivery of the data being sent/received over TCP.
You can experiment with TCP on a Linux PC using netcat, and capture the exchange using Wireshark or tcpdump.
Create a 'response' file containing 32 bytes:
echo 0123456789ABCDEFGHIJKL > response.txt
Start Wireshark, and filter on lo interface using filter tcp port 1234
Start a TCP server listening on TCP port 1234, which will send the content of response.txt upon receiving a connection from the client:
netcat -l 1234 < response.txt
In another console/shell, connect to the server listening on tcp/1234, and display what was received:
netcat localhost 1234
0123456789ABCDEFGHIJKL
On Wireshark, you should see the following Wireshark Network Capture, and be able to expand all frames/packets of the full exchange using the IBM Redbook as a reference.
Your 32 bytes of data will be in the payload section of a TCP packet sent by the server.
I'm trying to run tests on a simulated network I'm running on my machine and would like to get timing information on packets I'm sending and then receiving over local loopback.
When I run tcpdump -i lo I see two packets for every packet of data I send over local loopback: a data-carrying packet with a sequence number, and an associated ack packet. Each has only 1 timestamp associated with it.
I'd like to see when the data-carrying packet is sent and received, and when the ack packet is sent and received-- that is, 4 timestamps in total. I can't figure out how to do this in tcpdump no matter what Google searches I try or flags I pass it.
Right now I'm only getting 2 timestamps, one for each packet. I'm pretty sure they are both receive times for the packets.
I could probably run this test using two different machines, but I don't have another one on hand right now, and if I did that the clock between the two wouldn't be synchronized perfectly so the timestamps would be off.
It turns out what I'm asking for here is impossible. When sending over local loopback, the kernel uses a purely software layer, so there are no TCP packets actually being sent.
This is actually true for using any device and sending to yourself-- the kernel automatically optimizes and doesn't actually use the hardware to send packets.
In order to get send and receive times, you need to route through some other external agent. Alternatively, you can pretend there are two different interfaces running on your computer using netns, then connect them using virtual ethernet (veth) and then log tcpdump data over that connection.
See this blog post on setting up a connected netns namespace.
I have a simple xbee network operating where there are a bunch of slaves operating remotely and all talking to one master, who is connected to the server computer. That works no problem.
The slaves all send their ID as part of the packet and I'd like to have the master deliberately send an Ack after a delay. I'm trying to figure out how to do this efficiently and it seems that the only plausible way that doesn't involve reprogramming the master before each Ack is to send the Ack to all slaves and have them ignore the packet if it's not meant for them.
That solution is ok - I just can't figure out the command to use to do this. Is there some sort of Serial sendAll command? All of the devices are on the same ATID.
Typically in this situation, you would configure the master in API mode so you would get "Receive Explicit" frames with source addressing information, and could send with the "Transmit Explicit" frame type, and include addressing information in your frames.
If you use AT mode (transparent serial mode), then you're stuck having to change the DH and DL parameters on your coordinator every time you want to change who you send to. You should avoid using broadcast packets, since each one results in lots of network traffic (IIRC, each router will send the broadcast packet three times).
I do not know of a good XBee library on the Arduino, but it might be possible to port Digi's Open Source ANSI C XBee Host Library to that platform.
How is a packet received by a wireless devices with thousands of users/devices connected to the same network?
If we are using UDP, will it send the packets to all the devices such that only the authenticated devices will accept the packets and others would reject?
How does the situation change if we use TCP instead of UDP?
UDP and TCP are the same as they are higher layer protocols.
Majorly simplified, but the device opens a tunnel to a GSN (Gateway Serving Node) which is a server installed at the carrier. Which GSN to use is based on the APN (Access Point Name) supplied when the tunnel (PDP context) is requested. The tunnel is assigned an IP address at the GSN and that is the address used for IP communication. Packets will be filtered at the GSN and routed to the specific device. Traffic is tunneled between the GSN and the device using telecom specific protocols. Packets are not broadcast out to all devices and then filtered there.
Ps. I phrased the answer using GPRS terms. Other 2.5/3/4G protocols use the same structure but sometimes have different names.
what you mean by authenticated user?
are you concentrating in application level ? or at lower layers of the n/w?
even it is UDP , it should be thought of sending it to specific IP.even in complex n/w each s/m is an unique entity
Rohith Gowda , actually if you are concentrating on udp packets at Application level (either java, c# ...) u creates the packets for specific ip and sends to an IP,( which is the recivers ip) and the reciver have to grab it , i think you actually want this right? and no need to fear about others with different ip than what you are sending to, because you are in abstracted APP Layer, your doubt will be look after by lower layers.if you want an additional snooping proof just encode the data that you want to send
one Example is (in java)
DatagramPacket (UDP) can be created by invoking a new instance of
DatagramPacket(packet data [],offset ,length ,address* ,port* )
look at the last 2 params they specify the SeverAddress and the Port of transmit to the server
i think you are now clear that the destination server with the ip (Sever-address) listening at the particular port can grab it.
I am doing some experiment for which I need to collect Data from wlan driver.
I am interested in transmitting IEEE 802.11b Packets with more flexibility in terms of Data Rate, Packet Size etc.
Basically, I will have the laptop as the transmitter and I have built a custom receiver for IEEE 802.11b which would read the packets ( IEEE 802.11b 1/2/5.5 or 11Mbps) .
So, I am looking at some Linux tool which gives the option of setting these parameters while transmitting data.
I am thinking at commands like iwpriv to set the parameters for the wireless driver, and iperf commands to generate Traffic.
I am not sure, how to use them to achieve a Data traffic, say 1Mbps / and 1024 Bytes PSDU (Packet Size).
The receiver is a dedicated hardware ( not a Computer). Any suggestion or idea in this direction would be helpful.
Thanks
Use wireshark or pcap (via perl,python etc) to capture what you want.
You may be better off asking this on Server Fault. I found a couple of packet generators that look like they could do what you need but I'm by no means an expert.
packETH:
you can create and send any ethernet packet [...]
sending sequence of packets
delay between packets, number of packets to send
sending with max speed, approaching the teoretical boundary
change parameters while sending (change IP & mac address, UDP payload, 2 user defined bytes, etc.)
Ostantino:
Modify any field of any protocol (some protocols allow changing packet fields with every packet at run time e.g. changing IP/MAC addresses)
[...]
Configure stream rates, bursts, no. of packets
I found these in the Wireshare Wiki where there are a number of other tools that may help.