Colasoft Blog

http://www.networkcomputing.com/data-networking-management/10-free-network-analysis-tools/240163757?queryText=capsa

The article was written by Ericka Chickowski .She is an award-winning freelance writer, Ericka Chickowski specializes in coverage of information technology and business innovation. She has focused on information security for the better part of a decade and regularly writes about the security industry as a contributor to Dark Reading. Chickowski’s perspectives on business and technology have also appeared in dozens of trade and consumer magazines, includingChannel Insider, Consumers Digest,  Entrepreneur,  InformationWeek, Network Computing and SC Magazine.(Information from http://www.networkcomputing.com)

Ericka Chickowski  recommended 10 free network analysis tools in her article,the first one is Capsa Free.

This is how Ericka Chickowski describes Capsa Free.

“Capsa Free is an network analyzer designed for monitoring, troubleshooting and analysis, Capsa Freefrom Colasoft provides the capability to identify and monitor more than 300 different protocols. Users can record network profiles, create customizable reports and set customizable alarm trigger combinations. Additionally, Capsa offers MSN and Yahoo Messenger monitoring statistics, email monitoring and auto-saving of email content and an easy-to-use TCP timing sequence chart.” (Actually Capsa can  identify and monitor more than 400 different protocols now.)

Thanks Ericka, Thanks all the people who like Capsa.

Although Capsa network analyzer supports more than 160 protocols, there are still circumstances that you need add your private protocol rules. For example, you have a special service using a private TCP port in the network, and you want Capsa to recognize it. Or a protocol uses non-standard port. This document is to show you how to create your own custom protocols and edit built-in protocols as your need.
Create Custom Protocols
If you want to create a private protocol rule, follow the instructions below.
Step 1, run Capsa network analyzer. On the Start Page, click the Menu button (on the top-left corner). Choose Local Engine Settings -> Custom Protocol from the menu.
Step 2, on the Custom Protocol window, you can click the Add… button to create a custom protocol. For example, you are testing a new protocol, which uses TCP port 8080. You can just click Add, and type in protocol name, short name and port number, and choose a color for the protocol on the new dialog box. Then click OK to save the custom protocol.

Note: if the capture is running, you need to go back to the start page. Otherwise the Add button and Edit button will be grayed out.
Edit Protocols
If you use non-standard protocols in your network, for example, DNS isn’t on port 53 (TCP or UDP), or HTTP isn’t on TCP port 80, you should modify the default port number for these two built-in protocols. Or Capsa will recognize them as TCP/UDP Other type. Let’s make an example that HTTP uses TCP port 8080, rather than port 80.
Step 1, open the Custom Protocol window, type in http in the search box.
Step 2, double-click on the HTTP protocol item, and modify its port number to 8080 in the dialog box. Click OK to save.

Now if you start a capture, or replay a packet file, all packets using TCP port 81 will be labeled as HTTP protocol. On the Custom Protocol window, you can create private protocols on TCP/UDP ports, IP protocol type, and Ethernet type. TCP and UDP port numbers are used more often rather than the other two. And also you can use the Import button and Export button to back up your private protocols.

FAQ: Why the Add/Edit/Delete buttons of the Custom Protocol window are grayed out?
You are not allowed to change protocol rules while there is a capture running because the changes could crash the program. If you need to add/edit protocol rules, you need stop the capture and go back to the Start Page (if you run multiple instances, you need to close all others). Then click on the Menu button on the top-left corner of the Start Page, and choose Local Engine Settings > Custom Protocol to open the Custom Protocol window. Now you will find the buttons are clickable.

In computing, a protocol is a set of rules which is used by computers to communicate with each other across a network. A protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication. Protocols may be implemented by hardware, software, or a combination of the two. At the lowest level, a protocol defines the behavior of a hardware connection. A protocol is a formal description of message formats and the rules for exchanging those messages.

Today, there are many universities or institutes opening training section of network protocols. More and more people interested in computer programming are learning network protocols. They get training, have books or videos, they are fabulous about protocols. Network protocol analyzer is regarded as the best tool to help improve network protocols learning and teaching. There are many people using Wireshark to help learn or teach network protocols, Colasoft Capsa can also do this, and maybe better.

Now, let’s see how Capsa helps to improve network protocols learning and teaching in a more graphical and intuitive way.

Protocol decoding is the basic functionality as well. There is a Packet tab, which collect all captured packets or traffic. Select a packet and we can see its hex digits as well as the meaning of each field. The figure below shows the structure of an ARP packet. This makes it easy to understand how the packet is encapsulated according to its protocol rule.

For more complicated study such as how to establish a TCP connection by a three-way handshake, how to close a TCP connection, how the window size changes, and how to calculate the TCP SEQ number and ACK number, the Time Sequence functionality is helpful and intuitive. The Time Sequence tab displays the packet movement of a TCP conversation with two-direction arrows. The following figure sketches a complete process of a TCP conversation, from connection establishment to connection close. The columns on the left side of the arrows show the calculation of sender’s SEQ and ACK numbers. And also we can see the window size. On the right-side of the arrows, they are the receivers’.

Furthermore, for scientific research in network communication and protocols, we may need to create protocols of our own. Colasoft Capsa allows us to customize protocols. It’s very easy to create a protocol rule of TCP, UDP, IP and Ethernet II. See figure below.

Colasoft Capsa is a powerful protocol analyzer shipped with four powerful tools-packet builder, packet player, ping tool and mac scanner. The packet builder helps teachers and rookies to create or build packets like ARP, IP and TCP packets. The packet player can be used to send packets into the network to test the network. You can also import packet files captured by other network sniffers as well. With the assistance of network protocol sniffer tools, the theories on the book will no longer be dry and boring. Let Caps help you dig into the micro network world.