LAN Analyzer and Protocol Decoder - CommView

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About CommView
What's New
Using the Program
Selecting Network Interface for Monitoring
Latest IP Connections
Viewing Logs
Advanced Rules
Reconstructing TCP Sessions
Reconstructing UDP Streams
Searching Packets
Statistics and Reports
Using Aliases
Packet Generator
Visual Packet Builder
NIC Vendor Identifier
Using Remote Agent
Capturing Loopback Traffic
Port Reference
Setting Options
Frequently Asked Questions
VoIP Analysis
Working with VoIP Analyzer
SIP and H.323 Sessions
RTP Streams
Call Logging
Call Playback
Viewing VoIP Logs
Working with Lists in VoIP Analyzer
NVF Files
Advanced Topics
Capturing High Volume Traffic
Working with Multiple Instances
Running CommView in Invisible Mode
Command Line Parameters
Exchanging Data with Your Application
Custom Decoding
CommView Log Files Format
Sales and Support

Capturing Loopback Traffic

CommView allows you to capture traffic on the loopback interface. To start monitoring the loopback interface, select it from the drop-down list in the toolbar.

Loopback packets are the packets sent/received within the same computer, i.e. self-addressed packets. Typically, there is virtually no loopback traffic on the standard PC. However, loopback traffic is widely used by software developers for debugging network-related applications. Therefore, CommView's loopback capturing functionality is targeted primarily at this user group.

When you capture loopback traffic, the packets look exactly as any other network packets, except that the checksums are not computed. Please pay attention to the following peculiarities when capturing loopback traffic:

· CommView captures loopback traffic on all of the local IP addresses. This always includes, but may also include the IP addresses of your Ethernet adapters, e.g.
· ICMP packets cannot be captured. Other IP protocols can (TCP, UDP, etc.).
· Only successfully sent/received packets are captured. For example, if a connection attempt fails because the destination port is closed, you will not see any SYN / RST packets.
· Sessions are silently closed; no FIN packets are captured.