Capture Dynamic IP addresses and Their Applications

Source: Heiji

I. Dynamic Allocation of IP addresses and IP addresses

1. Basic concepts of IP addresses

The Internet relies on TCP/IP protocol to interconnect different hardware structures, operating systems, and network systems around the world. On the Internet, each node depends on a unique IP address to distinguish and connect with each other. An IP address is a 32-bit binary address consisting of four eight-bit fields. Each field is separated by a point number to identify the TCP/IP host.

Each IP address consists of a network ID and a host ID. The network ID identifies all hosts on the same physical network, and the host ID identifies each host on the physical network, therefore, every computer on the Internet is identified by its unique IP address.

IP addresses constitute the foundation of the entire Internet. It is so important that each networked computer has no right to set its own IP address, there is a unified organization-IANA is responsible for assigning a unique network ID to the requested organization, and the Organization can assign a unique host ID to each host in its own network, just as an organization does not have the right to decide its street name and house number in the city, it can decide its own office numbers.

2. static IP and dynamic IP

An IP address is a 32-bit binary address. In theory, there are about 4 billion possible address combinations (Power 32 of 2), which seems to be a large address space. In fact, IP addresses can be divided into A (7-bit network ID and 24-bit host ID) based on the network ID and host ID rules) B (14-bit network ID and 16-bit host ID), C (21-bit network ID and 8-bit host ID), due to historical reasons and technical development differences, class A addresses and Class B addresses are almost exhausted. Currently, only class C addresses can be allocated to organizations around the world. Therefore, IP addresses are a very important network resource.
For an organization that has set up Internet services, since its hosts open access services such as WWW, FTP, and e-mail, a fixed IP address is usually published to the outside world, to facilitate user access. Of course, Digital IP addresses are not easy to remember and recognize. People are more accustomed to accessing hosts through domain names, and domain names still need to be translated into IP addresses by domain name servers (DNS. For example, if your home address is www.myhost.com, you can easily remember and use it, and the Domain Name Server will translate the domain name into 101.12.123.234, which is your real address on the Internet.

For most dial-up Internet users, it is very undesirable to assign a fixed IP address (static IP address) to each user due to the discrete time and space on the Internet, this will cause a great waste of IP Address resources. Therefore, these users usually obtain a dynamic IP address every time they dial the ISP's host. This address is certainly not arbitrary, it is an address in the valid range of the network ID and host ID applied by the ISP. The IP addresses of the dial-up users for any two connections may be different, but the IP addresses remain unchanged during each connection time.

Ii. Point-to-Point TCP/IP connection

1. Point-to-Point TCP/IP connection and IP address

A computer running the TCP/IP protocol to access the Internet must have a unique IP address to communicate with other computers on the Internet. In fact, Internet connections can be described by four elements at any time: source IP address, source IP address port number, destination IP address, and destination IP address port number.

2. Indirect Implementation of point-to-point TCP/IP connections

Most internet users automatically obtain a dynamic IP address each time they access the Internet, which makes it difficult to establish a direct and convenient point-to-point TCP/IP connection between the two computers. The solution is to connect through indirect means, that is, both Parties log on to a service-providing host at the same time, and the host establishes indirect connections between the two parties, this method is widely used in network phones, network paging, and online games. With the maturity and development of technology, this network connection service can provide services such as network conferences, multi-party calls, and multi-party games, which has already broken through the limitations of Dual-host connection.

3. Direct Implementation of point-to-point TCP/IP connection

There are a lot of software that supports direct TCP/IP connections, such as Microsoft's network call software NetMeeting. The only premise is that both parties must obtain the dynamic IP addresses of the other party when connecting to the Internet, or, more simply, you only need to know the IP address of the called party, which is similar to knowing the called party's phone number to establish a telephone contact. Therefore, the key issue is to capture and exchange their respective Dynamic IP addresses, or capture and publish their own dynamic IP addresses to wait for the call and establish a connection.
3. Capture and publish Dynamic IP addresses

1. Capture Dynamic IP addresses

There are many methods and tools to capture Dynamic IP addresses. Windows 95/98 provides an IP configuration (WINIPCFG) utility by clicking "start-run ", in the "open" box, type: winipcfg. After the program window appears, you can click "details" to view details. The IP configuration utility allows users or administrators to view the current IP address and other useful information related to network configuration, including the host name, DNS server, IP address, and network mask. You can reset one or more IP addresses. The "release" or "Update" button releases or updates an IP address. To release or update all IP addresses, click "release all" or "update all ". Other tools can also query the local IP address.

2. Release of Dynamic IP addresses

You can update the obtained Dynamic IP address to your home page, so that all visitors can call the home page owner through this address to establish a point-to-point TCP/IP connection.

4. Dynamic IP address capturing and publishing tool-DynamIP

Once you understand the principles, you can use tools to complete this process. DynamIP is a good tool for dynamic capturing and publishing. DynamIP provides the following functions:

1. DUN/RAS Dialer with Event Driven Program Launcher: an Event-Driven dial-up tool that can be set based on user requirements or automatically and periodically, in addition, other applications can be run/closed under the drive of events such as "new connection establishment" or "connection termination". connections can be automatically terminated when the network traffic falls below the set value, this is especially useful for unattended downloading of large software.

2. Uploader (Dynamic IP address poster): file upload tool (Dynamic IP address publishing ). DynamIP can publish your dynamic IP address on a specified Web page and automatically upload the page to the server. Of course, it can also be used to update and upload any file, for example, to regularly upload a graphic file, which is automatically taken on a regular basis using a digital camera, so the Home Page becomes a live video page.

3. DIPS Client: DIPS Client software. DIPS (Dynamic IP Server) is short for Dynamic IP Server. After applying for a free account, the Dynamic IP server can display a URL on the home page pointing to your dynamic IP address in the form of: http://postmodem.com/dips/ <your account name>.

This function allows online users to access your local homepage through this URL. This is a Web server installed on a local host (such as a personal Web Server ). This feature is especially important when you need to debug the home page or you cannot find a free home page server that is satisfactory, or you think it is too time-consuming to upload the home page, the current virtual Domain Name Service is different from that, the virtual Domain Name Service requires that your home page be placed on the Home Page Server with a fixed domain name before transferring access can be provided, the Dynamic IP server can track your dynamic IP Address at any time and transfer visitors to your local Web server. As long as you connect to the Internet and your local Web server is running, DynamIP can automatically determine whether your DIPS information needs to be updated to the dynamic IP server. With DIPS, you can chat on the Web without uploading any files.

4. POP mail checker: Check the email address. You can check up to five different POP3 accounts and send a visual or audible message to the new email, automatically run the e-mail client to obtain the mail.

5. IP chat: point-to-point IP chat, similar to IRC, but does not require any IRC server. DynamIP can be scanned within the specified IP address range. You can broadcast messages to all chat members or specific IP addresses, you can greet other chat members to attract their attention and establish a private chat. DynamIP supports Microsoft's network telephone software MS NetMeeting.

6. WEBchat: Web chat. Visitors on your home page can use a browser to directly talk to you. Even if the other party does not install DynamIP, the page will be dynamically updated by DynamIP. the browser must support forms, Netscape, and Internet Explorer, forms is undoubtedly supported. Visitors can enter a statement in forms and then press the submit button to send the statement to your computer (Dynamic IP captured by DynamIP ). You can work with function 3 to implement local Web chat without uploading the home page to any server.

7. HTTPscan: HTTP scan. DynamIP can scan within a specified IP address range and generate a list Of all searched HTTP servers in hypertext file format. One of the purposes is that when you chat with someone through a point-to-point IP address, you can access the recipient's home page immediately.

8. PC Clock Synchronizer: Clock synchronization. DynamIP can get accurate dates and times from the NTP server to calibrate your machine clock, and can also be used to partially solve the problem of "Millennium worm.

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V. Install and set DynamIP

1. Install DynamIP

The installation of DynamIP has only one condition, that is, your Windows system must have the VB6.0 Runtime Library-MSVBVM60.DLL. This file is not included in the DynamIP software package. The user downloads it from the official website of Microsoft. The file name is vbrun60new.exe. It is an automatic installation file and the file length is 1 MB.

2. DynamIP settings

The basic principle of DynamIP is very simple. DynamIP will update a local file using parameters in the Template file (Template), which contains your current dynamic IP address, dynamIP then automatically uploads the file to your personal homepage server, so other users accessing your homepage can use the dynamic IP address information on the page to establish a connection with you to implement various network applications; or, DynamIPS updates your DIPS information to the dynamic IP server. All users accessing the server can be transferred to your local Web server. Therefore, when setting and preparing DynamIP, all work is carried out around this template file and your dynamic IP address.

The main function of DynamIP is the Uploader file upload tool (Dynamic IP address publishing). This article will take this as an example to introduce the settings of DynamIP. the settings of other functions are similar. Run DynamIP and select setup-uploader to enter the setting window. The parameters are as follows:

Active: enable/disable this service;

Remote Host: Specifies the FTP Host address of your home page. Do not enter the path on the Host;

Login: Your FTP account name;

Password: Your FTP account Password. These three parameters allow DynamIP to log on to your FTP host and automatically upload updated files. Generally, the host address of the home page is filled in.

Template Online: Online Template file, which will be generated