What Is a Socket?
This section describes what is a socket - An concept represents one end-point of a two-way communication link between two programs running on the Internet network.
Socket: An concept represents one end-point of a two-way communication
link between two programs running on the Internet network.
Internet Address: A unique number to identify each computer system on
Port: A number representing an entry point of on a computer system on
the Internet, where a two-way communication link can be established.
Local System: The computer system at this end of a two-way communication
Remote System: The computer system at the other end of a two-way
A two-way communication link on the Internet involves:
- Two computer systems, each has its own Internet address.
- A port number on each computer system that is used only by this
- An application program on each computer system that uses this
- A socket object created in the application program that represents
this communication link.
- The application program can use the socket as a logical input or
output device to receive or send data from or to the application program
running at the other end of the communication link.
- The application program can also query the socket for information
about the communication link, like: The Internet address and port number
at this end of the communication link; The Internet address and port number
at the other end of the communication link.
The following diagram illustrates how an application program can use a socket
to talk with other application programs running on another computer system
through a two-way communication link on the Internet:
Computer System I Computer System II
i/o |Address a| Internet |Address b| i/o
App. A<--->Socket|Port 1 |<-------------->| Port 2|Socket<--->App. X
Table of Contents
About This JDK Tutorial Book
JDK (Java Development Kit)
Java Date-Time API
Date, Time and Calendar Classes
Date and Time Object and String Conversion
Number Object and Numeric String Conversion
Locales, Localization Methods and Resource Bundles
Calling and Importing Classes Defined in Unnamed Packages
HashSet, Vector, HashMap and Collection Classes
Character Set Encoding Classes and Methods
Character Set Encoding Maps
Encoding Conversion Programs for Encoded Text Files
►Socket Network Communication
►What Is a Socket?
Establishing a Socket Communication Link
ReverseEchoer.java - A Simple Server Socket Application
SocketClient.java - A Simple Client Socket Application
ReverseEchoServer.java - A Multi-Connection Socket Server
Binding Sockets to Specific Ports
Datagram Network Communication
DOM (Document Object Model) - API for XML Files
SAX (Simple API for XML)
DTD (Document Type Definition) - XML Validation
XSD (XML Schema Definition) - XML Validation
XSL (Extensible Stylesheet Language)
Message Digest Algorithm Implementations in JDK
Private key and Public Key Pair Generation
PKCS#8/X.509 Private/Public Encoding Standards
Digital Signature Algorithm and Sample Program
"keytool" Commands and "keystore" Files
KeyStore and Certificate Classes
Secret Key Generation and Management
Cipher - Encryption and Decryption
The SSL (Secure Socket Layer) Protocol
SSL Socket Communication Testing Programs
SSL Client Authentication
HTTPS (Hypertext Transfer Protocol Secure)
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