working of wirwed modem

A Pocket PC can connect to the Internet via a wired modem in one of two ways. If the Pocket PC has a Bluetooth Internet connection, it can connect to a wired modem that has Bluetooth technology or a Bluetooth modem connected to it. If the Pocket PC has WiFi capabilities, it can connect to any wired modem that has a wireless router connected to it.
Connecting to a Wired Modem with Bluetooth
Pocket PCs with Bluetooth capability must first have the Bluetooth connection enabled. If the modem has Bluetooth built in, this should also be enabled. If the modem lacks Bluetooth, a seperate Bluetooth router can be purchased and connected via ethernet cable to broadband modems or directly to a dial-up modem with a standard phone line.If a modem has Bluetooth or a Bluetooth router connected but the Pocket PC lacks Bluetooth, a Bluetooth CompactFlash Type 2 adapter card can be purchased, giving the Pocket PC instant Bluetooth connectivity. The Pocket PC will discover the Bluetooth modem connection and connect to it.
Connecting to a Wired Modem with WiFi
This common way of connecting WiFi devices to a wired modem requires that a wireless router be connected to the wired modem. This wireless router connects to the modem via ethernet cable. The Internet connection is then made available to nearby wireless devices through a signal transmitted by the wireless router. Enabling WiFi on a Pocket PC with WiFi capabilities will allow the device to detect the wireless Internet connection and connect to it.Wireless routers may be encrypted and require a user name and password to access the secure wireless connection. When WiFi is enabled on a Pocket PC or PDA device, the device will scan for nearby networks and display both secured and unsecured networks. If the user lacks access to a secure network, the device can connect to public or unsecured wireless networks if they are available

various protocols

http://www.tutorialspoint.com/http/http_methods.htm

HTTP Message Structure

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Like most network protocols, HTTP uses the client-server model: An HTTP client opens a connection and sends a request message to an HTTP server; the server then returns a response message, usually containing the resource that was requested. After delivering the response, the server closes the connection. The format of the request and response messages are similar and will have following structure: An initial line CRLF Zero or more header lines CRLF A blank line ie. a CRLF An optioanl message body like file, query data or query output. Initial lines and headers should end in CRLF. Though you should gracefully handle lines ending in just LF. More exactly, CR and LF here mean ASCII values 13 and 10. Initial Line : Request The initial line is different for the request than for the response. A request line has three parts, separated by spaces: An HTTP Method Name The local path of the requested resource. The version of HTTP being used. Here is an exampple of initial line for Request Message. GET /path/to/file/index.html HTTP/1.0 GET is the most common HTTP method. Other methods could be POST, HEAD etc. The path is the part of the URL after the host name. This path is also called the request Uniform Resource Identifier (URI). A URI is like a URL, but more general. The HTTP version always takes the form "HTTP/x.x", uppercase. Initial Line : Response The initial response line, called the status line, also has three parts separated by spaces: The version of HTTP being used. A response status code that gives the result of the request. An English reason phrase describing the status code. Here is an exampple of initial line for Response Message. HTTP/1.0 200 OK or HTTP/1.0 404 Not Found Header Lines Header lines provide information about the request or response, or about the object sent in the message body. The header lines are in the usual text header format, which is: one line per header, of the form "Header-Name: value", ending with CRLF. It's the same format used for email and news postings, defined in RFC 822. A header line should end in CRLF, but you should handle LF correctly. The header name is not case-sensitive. Any number of spaces or tabs may be between the ":" and the value. Header lines beginning with space or tab are actually part of the previous header line, folded into multiple lines for easy reading. Here is an exampple of ione header line User-agent: Mozilla/3.0Gold or Last-Modified: Fri, 31 Dec 1999 23:59:59 GMT The Message Body An HTTP message may have a body of data sent after the header lines. In a response, this is where the requested resource is returned to the client (the most common use of the message body), or perhaps explanatory text if there's an error. In a request, this is where user-entered data or uploaded files are sent to the server. If an HTTP message includes a body, there are usually header lines in the message that describe the body. In particular: The Content-Type: header gives the MIME-type of the data in the body, such as text/html or image/gif. The Content-Length: header gives the number of bytes in the bod

message body

HTTP Message Structure

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Like most network protocols, HTTP uses the client-server model: An HTTP client opens a connection and sends a request message to an HTTP server; the server then returns a response message, usually containing the resource that was requested. After delivering the response, the server closes the connection. The format of the request and response messages are similar and will have following structure: An initial line CRLF Zero or more header lines CRLF A blank line ie. a CRLF An optioanl message body like file, query data or query output. Initial lines and headers should end in CRLF. Though you should gracefully handle lines ending in just LF. More exactly, CR and LF here mean ASCII values 13 and 10. Initial Line : Request The initial line is different for the request than for the response. A request line has three parts, separated by spaces: An HTTP Method Name The local path of the requested resource. The version of HTTP being used. Here is an exampple of initial line for Request Message. GET /path/to/file/index.html HTTP/1.0 GET is the most common HTTP method. Other methods could be POST, HEAD etc. The path is the part of the URL after the host name. This path is also called the request Uniform Resource Identifier (URI). A URI is like a URL, but more general. The HTTP version always takes the form "HTTP/x.x", uppercase. Initial Line : Response The initial response line, called the status line, also has three parts separated by spaces: The version of HTTP being used. A response status code that gives the result of the request. An English reason phrase describing the status code. Here is an exampple of initial line for Response Message. HTTP/1.0 200 OK or HTTP/1.0 404 Not Found Header Lines Header lines provide information about the request or response, or about the object sent in the message body. The header lines are in the usual text header format, which is: one line per header, of the form "Header-Name: value", ending with CRLF. It's the same format used for email and news postings, defined in RFC 822. A header line should end in CRLF, but you should handle LF correctly. The header name is not case-sensitive. Any number of spaces or tabs may be between the ":" and the value. Header lines beginning with space or tab are actually part of the previous header line, folded into multiple lines for easy reading. Here is an exampple of ione header line User-agent: Mozilla/3.0Gold or Last-Modified: Fri, 31 Dec 1999 23:59:59 GMT The Message Body An HTTP message may have a body of data sent after the header lines. In a response, this is where the requested resource is returned to the client (the most common use of the message body), or perhaps explanatory text if there's an error. In a request, this is where user-entered data or uploaded files are sent to the server. If an HTTP message includes a body, there are usually header lines in the message that describe the body. In particular: The Content-Type: header gives the MIME-type of the data in the body, such as text/html or image/gif. The Content-Length: header gives the number of bytes in the bod

ftp protocols link

http://www.windowsnetworking.com/articles_tutorials/Understanding-FTP-Protocol.html

http protocols

http://www.jmarshall.com/easy/http/

HTTP Overview

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HTTP stands for Hypertext Transfer Protocol. It is an TCP/IP based communication protocol which is used to deliver virtually all files and other data, collectively called resources, on the World Wide Web. These resources could be HTML files, image files, query results, or anything else. A browser is works as an HTTP client because it sends requests to an HTTP server which is called Web server. The Web Server then sends responses back to the client. The standard and default port for HTTP servers to listen on is 80 but it can be changed to any other port like 8080 etc. There are three important things about HTTP of which you should be aware: HTTP is connectionless: After a request is made, the client disconnects from the server and waits for a response. The server must re-establish the connection after it process the request. HTTP is media independent: Any type of data can be sent by HTTP as long as both the client and server know how to handle the data content. How content is handled is determined by the MIME specification. HTTP is stateless: This is a direct result of HTTP's being connectionless. The server and client are aware of each other only during a request. Afterwards, each forgets the other. For this reason neither the client nor the browser can retain information between different request across the web pages. Following diagram shows where HTTP Protocol fits in communication:

Mesh Topoloy

Mesh Topoloy

In this topology, every node has a dedicated point-to-point connection to every other node on the network. A fully connected mesh network has n(n-1)/2 channels to link 'n' devices. Therefore, every device on the network must have 'n-1' input/output (I/O) ports.

In mesh network, each node is directly connected to all nodes on the network. This type of network involves the concept of routes. In this type of network, each node may send message to destination through multiple paths. It means that each node of mesh network has several possible paths to send (or to receive) message, but in Bus, Star, Ring and Tree topologies each node has only one path.

Advantages

Mesh topology has the following advantages:

• It has multiple links, so if one route is blocked then other routes can be used for data communication.
• Each connection can have its own data load, so the traffic problem is eliminated.
• It ensures the data privacy or security, because every message travels along a dedicated link.
• Troubleshooting of this topology is easy as compared to other networks.
• Its performance is not affected with heavy load of data transmission.

Disadvantages

Mesh topology has the following disadvantages:

• It becomes very expensive because a large number of cabling and 110 ports are required.
• It is difficult to install.

Tree Topology

Tree Topology

In tree network, the nodes are connected to each other in such a way that forms a tree like structure. Typically to form a tree network, multiple star topologies are combined together. This type of network has combined features of bus and star topology.

On tree topology the hubs of each star topology are connected to the central hub that controls the entire network. However, some nodes can be directly connected to the central hub. The tree topology configuration is shown in figure below.

The central Hub in the tree network is an active hub. It contains a repeater (a hardware device), which re-generates the received bit patterns. The secondary hubs usually are passive hubs. The passive hub controls the nodes directly connected to it and exchange data to other devices connected to the other secondary hubs (or same hub) through the central hub. The secondary hub may also be active hub if another secondary hub is directly connected to it. The cable TV network is an example of tree topology, where main cable is divided into, branches and each branch is further divided into smaller branches and so on. The hub is used when a branch is created.

Advantages

The tree topology has the same advantages as star topology but it has some additional advantages. These are.

• It allows more devices to be connected to the central Hub.

Disadvantages

The tree topology also has the same disadvantages as star topology built has some additional disadvantages such as:

• It because more expansive because more hubs are required to install the network.

Hybrid Topology