Binding Sockets to Specific Ports
This section describes how to bind a socket to a specific port. Binding multiple client sockets to the same port is not allowed.
As I mentioned previously, I used a special socket constructor to allow the system
to bind the socket an un-specified local address and port number. This gives the
system the freedom to pickup an un-used port number. If I change SocketClient.java
Socket c = new Socket("localhost",8888);
Socket c = new Socket();
the first running instance of SocketClient will work, but additional running
instances will get the following error:
>java.net.BindException: Address already in use: JVM_Bind
Why? Because, at any given time, only one socket can be bound to a given port.
So, allowing the system to pick up a free local port number is a better idea.
However, the sockets created by the ServerSocket.accept() method seems to be
allowed to bind to the same local port. See the output of ReverseEchoServer.
When two or more client programs are connected to it, sockets created for
the connections are all bound to the same port number, 8888.
Exercise: Can you re-bind a bound socket to new port number?
Last update: 2014.
Table of Contents
About This JDK Tutorial Book
Downloading and Installing JDK 1.8.0 on Windows
Downloading and Installing JDK 1.7.0 on Windows
Downloading and Installing JDK 1.6.2 on Windows
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 - Secret Key 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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