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  • 서버-클라이언트가 있는 Java NIO(비차단 I/O) 예제 – java.nio.ByteBuffer 및 channel.Selector – Java NIO Vs. IO

서버-클라이언트가 있는 Java NIO(비차단 I/O) 예제 – java.nio.ByteBuffer 및 channel.Selector – Java NIO Vs. IO

게시 됨: 2021-08-06
서버-클라이언트가 있는 Java NIO(비차단 I:O) 예제 - CrunchifyNIOServer.java

Java NIO 는 내가 가장 좋아하는 주제입니다. 저는 지난 2년 동안 NIO와 함께 일해 왔으며 프로덕션 환경에서 이 코드를 자유롭게 사용할 수 있는 독자들을 위해 간단한 Server-Client code 를 공유하고 싶습니다.

JDK 1.4부터 NIO는 모든 Java 프로그래머가 사용자 정의 네이티브 코드를 처리하지 않고도 초고속 입출력을 구현할 수 있도록 만들어졌습니다. NIO는 내부적으로 모든 운영 체제에서 버퍼를 비우고 채우는 단순 I/O와 비교하여 java.nio.buffer 라이브러리를 사용합니다.

이 튜토리얼에서는 java.nio.channels 및 java.nio.channels.Selector 라이브러리를 살펴보겠습니다.

  • channels 은 파일 및 소켓과 같은 I/O 작업을 수행할 수 있는 엔터티에 대한 연결을 나타냅니다. 다중화, 비차단 I/O 작업을 위한 선택기를 정의 합니다.
  • 이 클래스의 open method 를 호출하여 selector 를 만들 수 있으며, 이 메서드는 시스템의 기본 선택기 공급자를 사용하여 새 선택기를 만듭니다.
API 세부 정보가 포함된 java.nio 패키지 설명

below questions 이 있는 경우 올바른 위치에 있습니다.

  • Java NIO를 시작하는 방법
  • Java NIO 및 Java NIO 튜토리얼이란 무엇입니까?
  • 비동기 자바 NIO
  • java nio 패키지의 정확한 용도는 무엇입니까?
  • 자바 NIO 튜토리얼
  • Java NIO로 고성능 I/O를 구현하는 방법

시작하자:

1 단계

  • port 1111 에서 연결을 여는 CrunchifyNIOServer.java 생성
  • isAcceptable() 을 사용하여 채널이 새 소켓 연결을 수락할 준비가 되었는지 확인합니다.
    • 그렇다면 연결하십시오
  • isReadable() 을 사용하여 채널이 읽을 준비가 되었는지 확인합니다.
    • 그렇다면 – 버퍼에서 읽고 Eclipse 콘솔에서 인쇄
  • 성을 얻으면 "crunchify"
    • 긴밀한 연결

2 단계

  • port 1111 에서 서버에 연결을 시도하는 CrunchifyNIOClient.java 를 만듭니다.
  • 5개의 회사 이름으로 ArrayList 생성
  • ArrayList를 반복하고 각 companyName을 서버로 보냅니다.
  • 작업 완료 후 연결 닫기

이 Java 코드를 살펴보십시오.

서버 코드 – CrunchifyNIOServer.java

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package crunchify . com . tutorials ;
 
import java . io . IOException ;
import java . net . InetSocketAddress ;
import java . nio . ByteBuffer ;
import java . nio . channels . SelectionKey ;
import java . nio . channels . Selector ;
import java . nio . channels . ServerSocketChannel ;
import java . nio . channels . SocketChannel ;
import java . util . Iterator ;
import java . util . Set ;
 
/**
* @author Crunchify.com
* Java NIO (Non-blocking I/O) with Server-Client Example - java.nio.ByteBuffer and channels.Selector
* This is CrunchifyNIOServer.java
*/
 
public class CrunchifyNIOServer {
 
@ SuppressWarnings ( "unused" )
public static void main ( String [ ] args ) throws IOException {
 
// Selector: A multiplexor of SelectableChannel objects.
// A selector may be created by invoking the open method of this class, which will use the system's default selector provider to create a new selector.
// A selector may also be created by invoking the openSelector method of a custom selector provider. A selector remains open until it is closed via its close method.
Selector selector = Selector . open ( ) ; // selector is open here
 
// ServerSocketChannel: A selectable channel for stream-oriented listening sockets.
// A server-socket channel is created by invoking the open method of this class.
// It is not possible to create a channel for an arbitrary, pre-existing ServerSocket.
ServerSocketChannel crunchifySocket = ServerSocketChannel . open ( ) ;
// InetSocketAddress: This class implements an IP Socket Address (IP address + port number) It can also be a pair (hostname + port number),
// in which case an attempt will be made to resolve the hostname.
// If resolution fails then the address is said to be unresolved but can still be used on some circumstances like connecting through a proxy.
InetSocketAddress crunchifyAddr = new InetSocketAddress ( "localhost" , 1111 ) ;
 
// Binds the channel's socket to a local address and configures the socket to listen for connections
crunchifySocket . bind ( crunchifyAddr ) ;
 
// Adjusts this channel's blocking mode.
crunchifySocket . configureBlocking ( false ) ;
 
int ops = crunchifySocket . validOps ( ) ;
// SelectionKey: A token representing the registration of a SelectableChannel with a Selector.
// A selection key is created each time a channel is registered with a selector.
// A key remains valid until it is cancelled by invoking its cancel method, by closing its channel, or by closing its selector.
SelectionKey selectKy = crunchifySocket . register ( selector , ops , null ) ;
 
// Infinite loop..
// Keep server running
while ( true ) {
 
log ( "I'm a server and I'm waiting for new connection and buffer select..." ) ;
// Selects a set of keys whose corresponding channels are ready for I/O operations
selector . select ( ) ;
 
// token representing the registration of a SelectableChannel with a Selector
Set < SelectionKey > crunchifyKeys = selector . selectedKeys ( ) ;
Iterator < SelectionKey > crunchifyIterator = crunchifyKeys . iterator ( ) ;
 
while ( crunchifyIterator . hasNext ( ) ) {
SelectionKey myKey = crunchifyIterator . next ( ) ;
 
// Tests whether this key's channel is ready to accept a new socket connection
if ( myKey . isAcceptable ( ) ) {
SocketChannel crunchifyClient = crunchifySocket . accept ( ) ;
 
// Adjusts this channel's blocking mode to false
crunchifyClient . configureBlocking ( false ) ;
 
// Operation-set bit for read operations
crunchifyClient . register ( selector , SelectionKey . OP_READ ) ;
log ( "Connection Accepted: " + crunchifyClient . getLocalAddress ( ) + "\n" ) ;
 
// Tests whether this key's channel is ready for reading
} else if ( myKey . isReadable ( ) ) {
SocketChannel crunchifyClient = ( SocketChannel ) myKey . channel ( ) ;
// ByteBuffer: A byte buffer.
// This class defines six categories of operations upon byte buffers:
// Absolute and relative get and put methods that read and write single bytes;
// Absolute and relative bulk get methods that transfer contiguous sequences of bytes from this buffer into an array;
ByteBuffer crunchifyBuffer = ByteBuffer . allocate ( 256 ) ;
crunchifyClient . read ( crunchifyBuffer ) ;
String result = new String ( crunchifyBuffer . array ( ) ) . trim ( ) ;
 
log ( "Message received: " + result ) ;
 
if ( result . equals ( "Crunchify.com" ) ) {
crunchifyClient . close ( ) ;
log ( "\nIt's time to close connection as we got last company name 'Crunchify'" ) ;
log ( "\nServer will keep running. Try running client again to establish new connection" ) ;
}
}
crunchifyIterator . remove ( ) ;
}
}
}
 
private static void log ( String str ) {
System . out . println ( str ) ;
}
}
 

클라이언트 코드 – CrunchifyNIOClient.java

서버-클라이언트가 있는 Java NIO(비차단 I:O) 예제 - CrunchifyNIOClient.java
Java
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package crunchify . com . tutorials ;
 
import java . io . IOException ;
import java . net . InetSocketAddress ;
import java . nio . ByteBuffer ;
import java . nio . channels . SocketChannel ;
import java . util . ArrayList ;
 
/**
* @author Crunchify.com
* Java NIO (Non-blocking I/O) with Server-Client Example - java.nio.ByteBuffer and channels.Selector
* This is CrunchifyNIOClient.java
*/
 
public class CrunchifyNIOClient {
 
public static void main ( String [ ] args ) throws IOException , InterruptedException {
 
InetSocketAddress crunchifyAddr = new InetSocketAddress ( "localhost" , 1111 ) ;
//  selectable channel for stream-oriented connecting sockets
SocketChannel crunchifyClient = SocketChannel . open ( crunchifyAddr ) ;
 
log ( "Connecting to Server on port 1111..." ) ;
 
ArrayList <String> companyDetails = new ArrayList <String> ( ) ;
 
// create a ArrayList with companyName list
companyDetails . add ( "Facebook" ) ;
companyDetails . add ( "Twitter" ) ;
companyDetails . add ( "IBM" ) ;
companyDetails . add ( "Google" ) ;
companyDetails . add ( "Crunchify" ) ;
 
for ( String companyName : companyDetails ) {
 
byte [ ] message = new String ( companyName ) . getBytes ( ) ;
ByteBuffer buffer = ByteBuffer . wrap ( message ) ;
crunchifyClient . write ( buffer ) ;
 
log ( "sending: " + companyName ) ;
buffer . clear ( ) ;
 
// wait for 2 seconds before sending next message
Thread . sleep ( 2000 ) ;
}
// close(): Closes this channel.
// If the channel has already been closed then this method returns immediately.
// Otherwise it marks the channel as closed and then invokes the implCloseChannel method in order to complete the close operation.
crunchifyClient . close ( ) ;
}
 
private static void log ( String str ) {
System . out . println ( str ) ;
}
}

서버 측 결과:

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I 'm a server and I' m waiting for new connection and buffer select . . .
Connection Accepted : / 127.0.0.1 : 1111
 
I 'm a server and <meta charset="utf-8"/>I' m waiting for new connection and buffer select . . .
Message received : Facebook
< meta charset = "utf-8" / > I 'm a server and <meta charset="utf-8"/>I' m waiting for new connection and buffer select . . .
Message received : Twitter
< meta charset = "utf-8" / > I 'm a server and <meta charset="utf-8"/>I' m waiting for new connection and buffer select . . .
Message received : IBM
< meta charset = "utf-8" / > I 'm a server and <meta charset="utf-8"/>I' m waiting for new connection and < a href = "https://crunchify.com/how-to-remove-duplicate-elements-from-csv-or-any-other-file-in-java/" target = "_blank" rel = "noreferrer noopener" > buffer < / a > select . . .
Message received : Google
< meta charset = "utf-8" / > I 'm a server and <meta charset="utf-8"/>I' m waiting for new connection and buffer select . . .
Message received : Crunchify
 
It 's time to <a href="https://crunchify.com/json-manipulation-in-java-examples/" target="_blank" rel="noreferrer noopener">close connection</a> as we got last company name ' Crunchify '
 
Server will keep running. Try running client again to establish new connection
<meta charset="utf-8"/>I' m a server and < meta charset = "utf-8" / > I ' m waiting for new connection and buffer select . . .

클라이언트 측 결과:

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Connecting to Server on port 1111...
sending : Facebook
sending : Twitter
sending : IBM
sending : Google
sending : Crunchify

몇 가지 자주 묻는 질문:

  1. 클라이언트에서 어떻게 지속적인 연결을 유지합니까?
    • socket.setKeepAlive(true); 클라이언트 측에서 연결을 유지합니다.
  2. 서버에 보낸 메시지에 대한 응답을 어떻게 읽습니까? 서버는 10초마다 메시지를 계속 생성합니다. 내 요청에 대한 응답을 읽기만 하면 됩니다. 내가 이해하는 바에 따르면 TCP는 레코드 끝 대신 데이터를 "스트리밍"합니다.
    • 클라이언트 서버 통신을 위해서는 프로토콜이 잘 정의되어 있어야 합니다. readLine() 호출은 모든 데이터가 반환될 때까지 차단되므로 사용하지 마십시오. Try reading bytes from the stream until -1 is returned.

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