packet catcher

Use the packet capture function in the test.Part1: in Windows, the packet capture tool WireSharkLinux has the following command: tcpdump-I eth0-s 0-w/home/nupt/log/2010112501.cap host 10.46.124.122-I indicates the network adapter-s indicates the file size-w specifies the file name written by packet capture information host specifies the target host use the ifconf

[Kaizige takes you to make a high imitation] High imitation and optimization of the Android version of "fried eggs" (1)-Introduction to reverse engineering and TcpDump packet capture, androidtcpdump Reprinted please indicate the source: http://blog.csdn.net/zhaokaiqiang1992 In a twinkling of an eye, the graduation season has arrived, and the four-year full and busy university is coming to an end. I am very much looking forward to my life after gra

During iOS development, various network access problems often occur. In the past, packet capture tools were not used, and many network problems were solved. Now, we have finished. This article provides two methods for packet capture: 1. Network Sharing + visual packet capture toolsBasic PrinciplesThe principle is relatively simple. iOS devices share the wireless

Let's start by recognizing what a packet loss is, and what kind of phenomenon is being lost to the network: Data is transmitted on the Internet on a packet-by-unit basis, with a packet of NK, no more, no less. That is to say, no matter how good the network line is, how strong the network equipment, your data will not be linear (like a telephone) tran

This article summarizes the good, from: http://hi.baidu.com/to_wait/blog/item/3e855931a5a51717eac4af22.html The TCP/IP protocol involves four layers: link layer, network layer, transmission layer, and application layer.The Ethernet data frame is at the link layer.IP packageAt the network layerTCP or UDP PacketsAt the transport layerData in TCP or UDP(Data) at the application layerTheirLink isData frame {IP packet {TCP or UDP

them in the/etc/services file of Linux.FTP-data 20/tcpFTP 21/tcpTelnet 23/tcpSMTP 25/tcp mailWWW 80/tcp HTTP # worldwideweb HTTPWWW 80/udp # Hypertext Transfer ProtocolPop-3 110/tcp # Pop Version 3Pop-3 110/udp In fact, the port number can be used with any services you like to specify, but in order to avoid "finding the wrong door" (unless you deliberately want to hide) people will use some of the more common services (wellKnownServices. However, in the TCP data transmission process, more than

, as determined by target: A. Continue to match next rule B. Make some changes to the packet C. Jump to another chain (that is, start by matching each rule in the chain sequentially) D. Returns the chain that raised the jump (that is, the next rule that continues to match the chain before the jump) E. Drop packet F. Receive packets (i.e. no longer continue to match down, return directly) G. Logging

origin:http://blog.csdn.net/e_wsq/article/details/12835457 For the TCP-based development of the communication program, there is a very important problem to be solved, that is, the packet and unpacking. Since I've been working on network communication programming (about three years), I've been thinking about and improving the way that packets and unpacking are addressed. Here's what I think about this question. If it's wrong, The wrong place, begged ev

Group First, let's look at the concept of the next grouping. The so-called grouping is to divide a packet into smaller packets. For example, for a 10GB packet, it is not always a one-time delivery of the past bar, but it is divided into a number of small packets sent past. Structure diagram for each block of data:File headers are typically descriptive data, such as source and destination addresses, data typ

Transferred from: http://cizixs.com/2018/01/13/linux-udp-packet-drop-debug?hmsr=toutiao.ioutm_medium=toutiao.ioutm_ Source=toutiao.ioRecent work encountered a server application UDP packet loss, in the process of reviewing a lot of information, summed up this article, for more people to refer to.Before we get started, we'll use a graph to explain the process of receiving network messages from a Linux system

The packet capture tool tcpdump in linux. The packet capture tool has two advantages: one is snort and the other is tcpdump. this time, we don't mention snort. Although the tool is powerful, it is complicated, and tcpdump is relatively simple. Tcpdumpwindows and tcpdump This article describes the packet capture tool in linux. The

Internet cafes often use DHCP services, such as the DCHP service provided by the diskless system server and the DCHP service of the router. First, the network administrator must understand the DHCP protocol packets, DHCP is a protocol designed by IETF to achieve automatic IP address configuration. The following types of DHCP packets are available. (1) DHCPDISCOVER (0 × 01), the first packet from the Client starting the DHCP process; (2) DHCPOFFER (0

Now we have to add port information to the UDP packet structure, which requires a new protocol. The simplest implementation is the UDP Protocol. Its format is almost in front of the data and the port number is added. A UDP packet is composed of two parts: "Header" and "data. The "Header" section mainly defines the sending and receiving ports, and the "data" section is the specific content. Then, put the ent

Introduction: The LLC sublayer read and forget, write in here convenient memory.Mac won't say it. LLC format Baidu.LLC Sub-layerThe LLC sublayer in the IEEE802.3 frame adds some other useful features in addition to defining traditional link-layer services. These features are provided by the DSAP, Ssap, and control fields.For example, the following three types of point-to-point transport services: Non-connected packet transport serviceThe curr

connection without packet loss. Then, I directly access and operate the sales system on the workstation in the Central Data Center. Everything is normal, it indicates that the network of the sales server and the central data center is normal. Is there a network problem at the sales office? Try to restart the switch at the sales office and test that the fault still exists.Are all computers in the sales office infected with viruses? I brought another l

This is a creation in Article, where the information may have evolved or changed. In the development of artificial customer service system with Golang encountered the problem of sticky bag, then what is sticky bag it? For example, we and the Client Convention data interaction format is a JSON-formatted string: {"Id": 1, "Name": "Golang", "message": "Message"} When the client sends the data to the server, if the server does not receive it in time, and the client sends a data, the server receives

I. Overview:After listening to the ASA video from yeslab's instructor QIN Ke, the FTP server is on the Outside and the FTP client is on the Inside. In this case, the active FTP server works normally because: ftp review can enable FTP to normally Modify FTP application layer data when traversing PAT), and enable FTP to actively initiate packets from Outside to Inside in active mode to pass the firewall smoothly. Because the configuration of PAT on the vro and FTP work normally, we plan to test wh

FFmpeg http://www.ffmpeg.club/Avpacket is ffmpeg used to store encoded video frame data, we analyze this structure, first put out the source code of Avpacket declaration in ffmpeg3.2:typedef struct AVPACKET {/*** A reference to the reference-counted buffer where the packet data is* stored.* could be NULL, Then the packet data isn't reference-counted.*/avbufferref *buf;/*** Presentation timestamp in avstream

First, let's look at the three-time handshake process for TCP1) First handshake: When establishing a connection, the client sends a SYN packet (SYN=J) to the server and enters the syn_sent state, waiting for the server to confirm; SYN: Synchronous sequence Number (Synchronize Sequence Numbers).2) Second handshake: The server receives the SYN packet, must confirm the customer's SYN (ACK=J+1), simultaneously

Qt packet abstraction based on TCP network program I have no experience before. When sending data packets, the packet header and other information are all implemented by redefining a struct. Different protocol packages have different structs. The result is as follows: how many upper-layer business protocol packages are there? I will re-define a new structure corresponding to the ending of the