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基于BIO的Java Socket通信詳解

發(fā)布時(shí)間：2020-09-17 12:05:04 來源：腳本之家 閱讀：194 作者：千與 欄目：編程語言

BIO，即阻塞IO，在基于Socket的消息通信過程中，Socket服務(wù)端向外部提供服務(wù)，而Socket客戶端可以建立到Socket服務(wù)端的連接，進(jìn)而發(fā)送請(qǐng)求數(shù)據(jù)，然后等待Socket服務(wù)端處理，并返回處理結(jié)果（響應(yīng)）。
基于BIO的通信，Socket服務(wù)端會(huì)發(fā)生阻塞，即在監(jiān)聽過程中每次accept到一個(gè)客戶端的Socket連接，就要處理這個(gè)請(qǐng)求，而此時(shí)其他連接過來的客戶端只能阻塞等待?？梢姡@種模式下Socket服務(wù)端的處理能力是非常有限的，客戶端也只能等待，直到服務(wù)端空閑時(shí)進(jìn)行請(qǐng)求的處理。

BIO通信實(shí)現(xiàn)

下面基于BIO模式，來實(shí)現(xiàn)一個(gè)簡單的Socket服務(wù)端與Socket客戶端進(jìn)行通信的邏輯，對(duì)這種通信方式有一個(gè)感性的認(rèn)識(shí)。具體邏輯描述如下：
1、Socket客戶端連接到Socket服務(wù)端，并發(fā)送數(shù)據(jù)“I am the client N.”；
2、Socket服務(wù)端，監(jiān)聽服務(wù)端口，并接收客戶端請(qǐng)求數(shù)據(jù)，如果請(qǐng)求數(shù)據(jù)以“I am the client”開頭，則響應(yīng)客戶端“I am the server, and you are the Nth client.”；

Socket服務(wù)端實(shí)現(xiàn)，代碼如下所示：

package org.shirdrn.java.communications.bio; 
 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.OutputStream; 
import java.net.ServerSocket; 
import java.net.Socket; 
 
/** 
 * 基于BIO的Socket服務(wù)器端 
 * 
 * @author shirdrn 
 */ 
public class SimpleBioTcpServer extends Thread { 
   
  /** 服務(wù)端口號(hào) */ 
  private int port = 8888; 
  /** 為客戶端分配編號(hào) */ 
  private static int sequence = 0; 
   
  public SimpleBioTcpServer(int port) { 
    this.port = port; 
  } 
   
  @Override 
  public void run() { 
    Socket socket = null; 
    try { 
      ServerSocket serverSocket = new ServerSocket(this.port); 
      while(true) { 
        socket = serverSocket.accept(); // 監(jiān)聽 
        this.handleMessage(socket); // 處理一個(gè)連接過來的客戶端請(qǐng)求 
      } 
    } catch (IOException e) { 
      e.printStackTrace(); 
    } 
  } 
   
  /** 
   * 處理一個(gè)客戶端socket連接 
   * @param socket 客戶端socket 
   * @throws IOException 
   */ 
  private void handleMessage(Socket socket) throws IOException { 
    InputStream in = socket.getInputStream(); // 流：客戶端->服務(wù)端（讀） 
    OutputStream out = socket.getOutputStream(); // 流：服務(wù)端->客戶端（寫） 
    int receiveBytes; 
    byte[] receiveBuffer = new byte[128]; 
    String clientMessage = ""; 
    if((receiveBytes=in.read(receiveBuffer))!=-1) { 
      clientMessage = new String(receiveBuffer, 0, receiveBytes); 
      if(clientMessage.startsWith("I am the client")) { 
        String serverResponseWords =  
          "I am the server, and you are the " + (++sequence) + "th client."; 
        out.write(serverResponseWords.getBytes()); 
      } 
    } 
    out.flush(); 
    System.out.println("Server: receives clientMessage->" + clientMessage); 
  } 
 
  public static void main(String[] args) { 
    SimpleBioTcpServer server = new SimpleBioTcpServer(1983); 
    server.start(); 
  } 
}

上述實(shí)現(xiàn)，沒有進(jìn)行復(fù)雜的異常處理。

Socket客戶端實(shí)現(xiàn)，代碼如下所示：

package org.shirdrn.java.communications.bio; 
 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.OutputStream; 
import java.net.Socket; 
import java.net.UnknownHostException; 
import java.util.Date; 
 
/** 
 * 基于BIO的Socket客戶端 
 * 
 * @author shirdrn 
 */ 
public class SimpleBioTcpClient { 
   
  private String ipAddress; 
  private int port; 
  private static int pos = 0; 
   
  public SimpleBioTcpClient() {} 
   
  public SimpleBioTcpClient(String ipAddress, int port) { 
    this.ipAddress = ipAddress; 
    this.port = port; 
  } 
 
  /** 
   * 連接Socket服務(wù)端，并模擬發(fā)送請(qǐng)求數(shù)據(jù) 
   * @param data 請(qǐng)求數(shù)據(jù) 
   */ 
  public void send(byte[] data) { 
    Socket socket = null; 
    OutputStream out = null; 
    InputStream in = null; 
    try { 
      socket = new Socket(this.ipAddress, this.port); // 連接 
      // 發(fā)送請(qǐng)求 
      out = socket.getOutputStream(); 
      out.write(data);  
      out.flush(); 
      // 接收響應(yīng) 
      in = socket.getInputStream(); 
      int totalBytes = 0; 
      int receiveBytes = 0; 
      byte[] receiveBuffer = new byte[128]; 
      if((receiveBytes=in.read(receiveBuffer))!=-1) { 
        totalBytes += receiveBytes; 
      } 
      String serverMessage = new String(receiveBuffer, 0, receiveBytes); 
      System.out.println("Client: receives serverMessage->" + serverMessage); 
    } catch (UnknownHostException e) { 
      e.printStackTrace(); 
    } catch (IOException e) { 
      e.printStackTrace(); 
    } catch (Exception e) { 
      e.printStackTrace(); 
    } finally { 
      try { 
        // 發(fā)送請(qǐng)求并接收到響應(yīng)，通信完成，關(guān)閉連接 
        out.close(); 
        in.close(); 
        socket.close(); 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
  } 
 
  public static void main(String[] args) { 
    int n = 1; 
    StringBuffer data = new StringBuffer(); 
    Date start = new Date(); 
    for(int i=0; i<n; i++) { 
      data.delete(0, data.length()); 
      data.append("I am the client ").append(++pos).append("."); 
      SimpleBioTcpClient client = new SimpleBioTcpClient("localhost", 1983); 
      client.send(data.toString().getBytes()); 
    } 
    Date end = new Date(); 
    long cost = end.getTime() - start.getTime(); 
    System.out.println(n + " requests cost " + cost + " ms."); 
  } 
}

首先啟動(dòng)Socket服務(wù)端進(jìn)程SimpleBioTcpServer，然后再運(yùn)行Socket客戶端SimpleBioTcpClient。可以看到，服務(wù)端接收到請(qǐng)求數(shù)據(jù)，然后響應(yīng)客戶端，客戶端接收到了服務(wù)端的響應(yīng)數(shù)據(jù)。

上述實(shí)現(xiàn)中，對(duì)于Socket客戶端和服務(wù)端都是一次寫入，并一次讀出，而在實(shí)際中如果每次通信過程中數(shù)據(jù)量特別大的話，服務(wù)器端是不可能接受的，可以在確定客戶端請(qǐng)求數(shù)據(jù)字節(jié)數(shù)的情況，循環(huán)來讀取并進(jìn)行處理。

另外，對(duì)于上述實(shí)現(xiàn)中流沒有進(jìn)行裝飾（Wrapped）處理，在實(shí)際中會(huì)有性能的損失，如不能緩沖等。

對(duì)于Socket服務(wù)端接收數(shù)據(jù)，如果可以使多次循環(huán)讀取到的字節(jié)數(shù)據(jù)通過一個(gè)可變長的字節(jié)緩沖區(qū)來存儲(chǔ)，就能方便多了，可是使用ByteArrayOutputStream，例如：

ByteArrayOutputStream data = new ByteArrayOutputStream(); 
data.write(receiveBuffer, totalBytes , totalBytes + receiveBytes);

BIO通信測(cè)試

下面測(cè)試一下大量請(qǐng)求的場景下，Socket服務(wù)端處理的效率。

第一種方式：通過for循環(huán)來啟動(dòng)5000個(gè)Socket客戶端，發(fā)送請(qǐng)求，代碼如下所示：

public static void main(String[] args) { 
  int n = 5000; 
  StringBuffer data = new StringBuffer(); 
  Date start = new Date(); 
  for(int i=0; i<n; i++) { 
    data.delete(0, data.length()); 
    data.append("I am the client ").append(++pos).append("."); 
    SimpleBioTcpClient client = new SimpleBioTcpClient("localhost", 1983); 
    client.send(data.toString().getBytes()); 
  } 
  Date end = new Date(); 
  long cost = end.getTime() - start.getTime(); 
  System.out.println(n + " requests cost " + cost + " ms."); 
}

經(jīng)過測(cè)試，大約需要9864ms，大概接近10s。

第二種方式：通過啟動(dòng)5000個(gè)獨(dú)立的客戶端線程，同時(shí)請(qǐng)求，服務(wù)端進(jìn)行計(jì)數(shù)：

package org.shirdrn.java.communications.bio; 
 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.OutputStream; 
import java.net.ServerSocket; 
import java.net.Socket; 
import java.net.UnknownHostException; 
import java.util.Date; 
 
/** 
 * 基于BIO的Socket通信測(cè)試 
 * 
 * @author shirdrn 
 */ 
public class SimpleBioTcpTest { 
   
  static int threadCount = 5000; 
   
  /** 
   * 基于BIO的Socket服務(wù)端進(jìn)程 
   * 
   * @author shirdrn 
   */ 
  static class SocketServer extends Thread { 
     
    /** 服務(wù)端口號(hào) */ 
    private int port = 8888; 
    /** 為客戶端分配編號(hào) */ 
    private static int sequence = 0; 
     
    public SocketServer(int port) { 
      this.port = port; 
    } 
     
    @Override 
    public void run() { 
      Socket socket = null; 
      int counter = 0; 
      try { 
        ServerSocket serverSocket = new ServerSocket(this.port); 
        boolean flag = false; 
        Date start = null; 
        while(true) { 
          socket = serverSocket.accept(); // 監(jiān)聽 
          // 有請(qǐng)求到來才開始計(jì)時(shí) 
          if(!flag) { 
            start = new Date(); 
            flag = true; 
          } 
          this.handleMessage(socket); // 處理一個(gè)連接過來的客戶端請(qǐng)求 
          if(++counter==threadCount) { 
            Date end = new Date(); 
            long last = end.getTime() - start.getTime(); 
            System.out.println(threadCount + " requests cost " + last + " ms."); 
          } 
        } 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
     
    /** 
     * 處理一個(gè)客戶端socket連接 
     * @param socket 客戶端socket 
     * @throws IOException 
     */ 
    private void handleMessage(Socket socket) throws IOException { 
      InputStream in = socket.getInputStream(); // 流：客戶端->服務(wù)端（讀） 
      OutputStream out = socket.getOutputStream(); // 流：服務(wù)端->客戶端（寫） 
      int receiveBytes; 
      byte[] receiveBuffer = new byte[128]; 
      String clientMessage = ""; 
      if((receiveBytes=in.read(receiveBuffer))!=-1) { 
        clientMessage = new String(receiveBuffer, 0, receiveBytes); 
        if(clientMessage.startsWith("I am the client")) { 
          String serverResponseWords =  
            "I am the server, and you are the " + (++sequence) + "th client."; 
          out.write(serverResponseWords.getBytes()); 
        } 
      } 
      out.flush(); 
      System.out.println("Server: receives clientMessage->" + clientMessage); 
    } 
  } 
   
  /** 
   * 基于BIO的Socket客戶端線程 
   * 
   * @author shirdrn 
   */ 
  static class SocketClient implements Runnable { 
     
    private String ipAddress; 
    private int port; 
    /** 待發(fā)送的請(qǐng)求數(shù)據(jù) */ 
    private String data; 
     
    public SocketClient(String ipAddress, int port) { 
      this.ipAddress = ipAddress; 
      this.port = port; 
    } 
 
    @Override 
    public void run() { 
      this.send();       
    } 
     
    /** 
     * 連接Socket服務(wù)端，并模擬發(fā)送請(qǐng)求數(shù)據(jù) 
     */ 
    public void send() { 
      Socket socket = null; 
      OutputStream out = null; 
      InputStream in = null; 
      try { 
        socket = new Socket(this.ipAddress, this.port); // 連接 
        // 發(fā)送請(qǐng)求 
        out = socket.getOutputStream(); 
        out.write(data.getBytes());  
        out.flush(); 
        // 接收響應(yīng) 
        in = socket.getInputStream(); 
        int totalBytes = 0; 
        int receiveBytes = 0; 
        byte[] receiveBuffer = new byte[128]; 
        if((receiveBytes=in.read(receiveBuffer))!=-1) { 
          totalBytes += receiveBytes; 
        } 
        String serverMessage = new String(receiveBuffer, 0, receiveBytes); 
        System.out.println("Client: receives serverMessage->" + serverMessage); 
      } catch (UnknownHostException e) { 
        e.printStackTrace(); 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } catch (Exception e) { 
        e.printStackTrace(); 
      } finally { 
        try { 
          // 發(fā)送請(qǐng)求并接收到響應(yīng)，通信完成，關(guān)閉連接 
          out.close(); 
          in.close(); 
          socket.close(); 
        } catch (IOException e) { 
          e.printStackTrace(); 
        } 
      } 
    } 
 
    public void setData(String data) { 
      this.data = data; 
    } 
  } 
 
  public static void main(String[] args) throws Exception { 
    SocketServer server = new SocketServer(1983); 
    server.start(); 
     
    Thread.sleep(3000); 
     
    for(int i=0; i<threadCount; i++) { 
      SocketClient client = new SocketClient("localhost", 1983); 
      client.setData("I am the client " + (i+1) + "."); 
      new Thread(client).start(); 
      Thread.sleep(0, 1); 
    }     
  } 
}

 經(jīng)過測(cè)試，大約需要7110ms，大概接近7s，沒有太大提高。

BIO通信改進(jìn)

通過上面的測(cè)試我們可以發(fā)現(xiàn)，在Socket服務(wù)端對(duì)來自客戶端的請(qǐng)求進(jìn)行處理時(shí)，會(huì)發(fā)生阻塞，嚴(yán)重地影響了能夠并發(fā)處理請(qǐng)求的效率。實(shí)際上，在Socket服務(wù)端接收來自客戶端連接能力的范圍內(nèi)，可以將接收請(qǐng)求獨(dú)立出來，從而在將處理請(qǐng)求獨(dú)立粗話來，通過一個(gè)請(qǐng)求一個(gè)線程處理的方式來解決上述問題。這樣，服務(wù)端是多處理線程對(duì)應(yīng)客戶端多請(qǐng)求，處理效率有一定程度的提高。

下面，通過單線程接收請(qǐng)求，然后委派線程池進(jìn)行多線程并發(fā)處理請(qǐng)求：

/** 
   * 基于BIO的Socket服務(wù)端進(jìn)程 
   * 
   * @author shirdrn 
   */ 
  static class SocketServer extends Thread { 
     
    /** 服務(wù)端口號(hào) */ 
    private int port = 8888; 
    /** 為客戶端分配編號(hào) */ 
    private static int sequence = 0; 
    /** 處理客戶端請(qǐng)求的線程池 */ 
    private ExecutorService pool; 
     
    public SocketServer(int port, int poolSize) { 
      this.port = port; 
      this.pool = Executors.newFixedThreadPool(poolSize); 
    } 
     
    @Override 
    public void run() { 
      Socket socket = null; 
      int counter = 0; 
      try { 
        ServerSocket serverSocket = new ServerSocket(this.port); 
        boolean flag = false; 
        Date start = null; 
        while(true) { 
          socket = serverSocket.accept(); // 監(jiān)聽 
          // 有請(qǐng)求到來才開始計(jì)時(shí) 
          if(!flag) { 
            start = new Date(); 
            flag = true; 
          } 
          // 將客戶端請(qǐng)求放入線程池處理 
          pool.execute(new RequestHandler(socket)); 
          if(++counter==threadCount) { 
            Date end = new Date(); 
            long last = end.getTime() - start.getTime(); 
            System.out.println(threadCount + " requests cost " + last + " ms."); 
          } 
        } 
      } catch (IOException e) { 
        e.printStackTrace(); 
      } 
    } 
     
    /** 
     * 客戶端請(qǐng)求處理線程類 
     * 
     * @author shirdrn 
     */ 
    class RequestHandler implements Runnable { 
 
      private Socket socket; 
       
      public RequestHandler(Socket socket) { 
        this.socket = socket; 
      } 
       
      @Override 
      public void run() { 
        try { 
          InputStream in = socket.getInputStream(); // 流：客戶端->服務(wù)端（讀） 
          OutputStream out = socket.getOutputStream(); // 流：服務(wù)端->客戶端（寫） 
          int receiveBytes; 
          byte[] receiveBuffer = new byte[128]; 
          String clientMessage = ""; 
          if((receiveBytes=in.read(receiveBuffer))!=-1) { 
            clientMessage = new String(receiveBuffer, 0, receiveBytes); 
            if(clientMessage.startsWith("I am the client")) { 
              String serverResponseWords =  
                "I am the server, and you are the " + (++sequence) + "th client."; 
              out.write(serverResponseWords.getBytes()); 
            } 
          } 
          out.flush(); 
          System.out.println("Server: receives clientMessage->" + clientMessage); 
        } catch (IOException e) { 
          e.printStackTrace(); 
        }         
      } 
    } 
  }

可見，這種改進(jìn)方式增強(qiáng)服務(wù)端處理請(qǐng)求的并發(fā)度，但是每一個(gè)請(qǐng)求都要由一個(gè)線程去處理，大量請(qǐng)求造成服務(wù)端啟動(dòng)大量進(jìn)程進(jìn)行處理，也是比較占用服務(wù)端資源的。

以上就是本文的全部內(nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持億速云。

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