packet

Parsing WiFi Packets (libpcap)

由 冷暖自知 提交于 2019-11-27 11:43:34
问题 I've been working on a way to have an OpenWRT router log WiFi probe requests to a MySQL db (it stores MAC address and RSSI info for each probe request packet along with other, router-specific data). After researching libpcap quite a bit, I've been able to cobble together a basic little program that simply sniffs packets on a monitor interface (mon0) using a filter expression ('wlan subtype probe-req') and then prints out the raw packets in hex. With the info that's available online on libpcap

JavaScript WebSockets with UDP?

由 丶灬走出姿态 提交于 2019-11-27 09:49:13
问题 I'm writing a JavaScript Application that has to receive a huge amount of data from other users. It is not important if some of this data gets lost. Is there some way of using JavaScript WebSockets with UDP instead of TCP? 回答1: No, it's not possible to have UDP communication within JavaScript. Sorry. 回答2: It sounds like what you're waiting for is WebRTC which is working it's way through the standards process. WebSockets, as other people have pointed out, run over TCP as a result of initiating

Does TCP send a SYN/ACK on every packet or only on the first connection?

由 不羁的心 提交于 2019-11-27 09:36:16
问题 I have a TCP server that listens for an incoming client, then sends it one packet of data every second. I was wondering, does the SYN/ACK packet only get sent on initial connection, so it looks like this: <client connect> SYN ACK DATA DATA DATA <client disconnect> Or does it get sent with every packet, like this? <client connect> SYN ACK DATA SYN ACK DATA SYN ACK DATA <client disconnect> Also, if it's the first case, are there any benefits of UDP over TCP if you just keep the connection open

python: how to send packets in multi thread and then the thread kill itself

由 十年热恋 提交于 2019-11-27 04:06:11
问题 I have a question. I'd like to send a continuous streams of byte to some host for certain amount of time (let's say 1 minute) using python. Here is my code so far: #! /usr/bin/env python import socket import thread import time IP = "192.168.0.2" PADDING = "a" * 1000 #assume the MTU is slighly above 1000 DATA = PADDING + "this is sentence number = " PORT = 14444 killed = False test_time = 60 #60 seconds of testing def send_data(): s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect

When will a TCP network packet be fragmented at the application layer?

由 和自甴很熟 提交于 2019-11-27 03:50:18
When will a TCP packet be fragmented at the application layer? When a TCP packet is sent from an application, will the recipient at the application layer ever receive the packet in two or more packets? If so, what conditions cause the packet to be divided. It seems like a packet won't be fragmented until it reaches the Ethernet (at the network layer) limit of 1500 bytes. But, that fragmentation will be transparent to the recipient at the application layer since the network layer will reassemble the fragments before sending the packet up to the next layer, right? It will be split when it hits a

checksum udp calculation python

由 心已入冬 提交于 2019-11-27 02:57:25
问题 I'd like to calculate the checksum of an UDP header packet I want to send: packetosend = """60 00 00 00 00 24 3a 40 20 02 c0 a8 01 50 00 01 00 00 00 00 00 00 09 38 20 02 c0 a8 01 50 00 01 00 00 00 00 00 00 09 6f""" so I need to join this utf-16 (not a problem) and calculate the checksum of this specific packet. How can I do that? Thanks! EDIT: Yes it's an IPv6 header for an ICMPv6 packet, anyways what I would like to know is the formula, and how it works. I'll give another example with an

What is the size of udp packets if i send 0 payload data in c#?

由 ￡可爱￡侵袭症＋ 提交于 2019-11-27 01:46:05
问题 I have figured out the maximum data before fragmentation between 2 endpoints using udp is 1472(other endpoints may vary). this states that mtu is 1500bytes and header overhead per packet is 28bytes.is it safe to assume that if i send 0 bytes data(payload), the actual data being transferred is 28bytes? im doing some bencchmark, so its crucial for me to know what happens in the channel. thanks. 回答1: The MTU is the maximum size of an IP packet that can be transmitted without fragmentation. IPv4

Identification of packets in a byte stream

由 故事扮演 提交于 2019-11-26 23:06:43
I'm having a bit of a problem with the communication to an accelerometer sensor. The sensor puts out about 8000 readings/second continuously. The sensor is plugged in to a usb port with an adaper and shows up as com4. My problem is that I can't seem to pick out the sensor reading packets from the byte stream. The packets have the size of five bytes and have the following format: High nibble Low nibble Byte 1 checksum, id for packet start X high Byte 2 X mid X low Byte 3 Y high Y mid Byte 4 Y low Z high Byte 5 Y mid Y low X, y, z is the acceleration. In the documentation for the sensor it

HTTP packet reconstruction

由 ≡放荡痞女 提交于 2019-11-26 23:05:05
问题 If I have a large HTTP packet which has been split up into a number of TCP packets, how can I reconstruct them back into a single HTTP packet? Basically, where in the packet do I look to tell when a HTTP packet is starting/ending? I can't seem to see any flags/fields in the TCP header that denote the start or end of the HTTP packet. EDIT: In follow up to the responses. If TCP manages the stream, how does it know when the stream starts and ends? Is that determined by the socket opening and

Android VpnService to capture packets won't capture packets

由 ◇◆丶佛笑我妖孽 提交于 2019-11-26 18:34:49
I been searching for my answer for a couple of hours now and I can't figure it out. Please help. What I want to do is to use the VpnService in Android to grab network packets like the application tPacketCapture I started by using the ToyVpn sample code from google and modifying it so I don't send the data to a server. However, I'm not sure if this is correct. My configure method uses the wlan ip address for binder.addAddress() before calling establish(). I am using a nexus 7 and I used "adb shell netcfg | grep wlan0" to get the address: wlan0 UP 192.168.0.6/24 0x00001043 10:bf:48:bf:5f:9d And
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