wireshark filter port with code examples

Wireshark is a popular open-source packet analyzer that allows users to capture and analyze network traffic. One of the powerful features of Wireshark is the ability to filter captured packets using a wide range of criteria, including the source and destination ports. In this article, we will discuss how to filter network traffic by port using Wireshark and provide some code examples.

Before we begin, it's important to understand the concept of ports in the context of network communication. In the Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), a port is a 16-bit number that identifies a specific process running on a host. When a host sends or receives data, it uses a specific port number to identify the process that is sending or receiving the data. For example, when a web browser sends a request to a web server, it typically uses port 80 for the request.

Wireshark provides several ways to filter network traffic by port. The simplest way is to use the filter bar at the top of the Wireshark window. To filter traffic by a specific port, you can enter "tcp.port == 80" (without the quotes) in the filter bar. This will show only the packets that have a source or destination port of 80. Similarly, you can filter traffic by a specific UDP port by using "udp.port == 53" (without the quotes).

Another way to filter traffic by port is to use the "Filter Expression" dialog box. To access this dialog box, go to the "Analyze" menu and select "Display Filter." In the dialog box, you can enter a filter expression such as "tcp.port == 80" or "udp.port == 53." You can also use logical operators such as "or" and "and" to create more complex filters. For example, to filter traffic that has a source or destination port of 80 or 443, you can use the filter expression "tcp.port == 80 or tcp.port == 443."

In addition to filtering traffic by a specific port, you can also filter traffic by a range of ports. For example, to filter traffic that has a source or destination port between 80 and 90, you can use the filter expression "tcp.port >= 80 and tcp.port <= 90."

It's also possible to filter by both source and destination port. For example, to filter traffic that has a source port of 80 and a destination port of 53, you can use the filter expression "tcp.srcport == 80 and udp.dstport == 53"

It's also possible to filter traffic by port using Lua script, here is an example:

-- filter for packets with a source or destination port of 80
local filter = "tcp.port == 80 or udp.port == 80"

In conclusion, Wireshark provides a powerful and flexible filtering mechanism that allows users to capture and analyze network traffic based on various criteria, including the source and destination ports. By understanding the concept of ports and using the filter bar, the "Filter Expression" dialog box, logical operators, and Lua script, you can effectively filter network traffic and gain valuable insights into your network's behavior.

In addition to filtering traffic by port, Wireshark also provides several other filtering options that can be used to capture and analyze network traffic. Some of the most commonly used filters include:

  • IP address: You can filter traffic based on the source or destination IP address. For example, to filter traffic that has a source IP address of 192.168.1.100, you can use the filter expression "ip.src == 192.168.1.100".

  • Protocol: You can filter traffic based on the protocol used to transfer the data. For example, to filter traffic that uses the TCP protocol, you can use the filter expression "tcp".

  • Ethernet: You can filter traffic based on the Ethernet protocol. For example, to filter traffic that uses the Ethernet II protocol, you can use the filter expression "eth.type == 0x0800".

  • DNS: You can filter traffic based on the DNS protocol. For example, to filter DNS query traffic, you can use the filter expression "dns.flags.response == 0".

  • HTTP: You can filter traffic based on the HTTP protocol. For example, to filter HTTP GET requests, you can use the filter expression "http.request.method == GET".

  • DHCP: You can filter traffic based on the DHCP protocol. For example, to filter DHCP discover requests, you can use the filter expression "bootp.option.dhcp == 1"

  • IPV6: You can filter traffic based on the IPV6 protocol. For example, to filter ICMPv6 traffic, you can use the filter expression "icmp6"

  • Wi-Fi : You can filter traffic based on the Wi-Fi protocol. For example, to filter traffic that uses the IEEE 802.11 protocol, you can use the filter expression "wlan"

Another powerful feature of Wireshark is the ability to create and save custom filters. You can create a custom filter by entering a filter expression in the filter bar or the "Filter Expression" dialog box, and then saving it for future use. Custom filters can be saved in the "Capture Filters" or "Display Filters" sections of the "Capture Options" dialog box.

In addition to Wireshark, there are other packet analyzers available such as tcpdump, Microsoft Message Analyzer, and others. Some of these tools may have slightly different syntax for filters and options, but the concepts are similar.

In conclusion, Wireshark is a powerful tool that allows you to capture and analyze network traffic based on various criteria. By understanding the different filtering options available, such as port, IP address, protocol, and more, you can effectively capture and analyze the network traffic that is relevant to your needs. Additionally, it's important to note that Wireshark isn't the only packet analyzer out there, and you can use similar tools that might suit your needs better.

Popular questions

  1. What is a port in the context of network communication?
    A port is a 16-bit number that identifies a specific process running on a host. When a host sends or receives data, it uses a specific port number to identify the process that is sending or receiving the data.

  2. How can I filter network traffic by port using Wireshark?
    One way to filter network traffic by port using Wireshark is to use the filter bar at the top of the Wireshark window. To filter traffic by a specific port, you can enter "tcp.port == 80" (without the quotes) in the filter bar. This will show only the packets that have a source or destination port of 80. Another way is to use the "Filter Expression" dialog box, where you can enter a filter expression such as "tcp.port == 80" or "udp.port == 53"

  3. Can I filter traffic by a range of ports using Wireshark?
    Yes, it is possible to filter traffic by a range of ports using Wireshark. For example, to filter traffic that has a source or destination port between 80 and 90, you can use the filter expression "tcp.port >= 80 and tcp.port <= 90."

  4. Can I filter traffic by both source and destination port?
    Yes, it's possible to filter traffic by both source and destination port. For example, to filter traffic that has a source port of 80 and a destination port of 53, you can use the filter expression "tcp.srcport == 80 and udp.dstport == 53"

  5. Can I filter traffic by port using Lua script in Wireshark?
    Yes, it's possible to filter traffic by port using Lua script in Wireshark. For example, to filter for packets with a source or destination port of 80, you can use the following script:

local filter = "tcp.port == 80 or udp.port == 80"

It's important to note that you will need to have Lua support enabled in Wireshark to use this feature.

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