学步园

最近需要进行网络传输大文件，于是对基于socket的文件传输作了一个初步的了解。在一位网友提供的程序基础上，俺进行了一些加工，采用了缓冲输入/输出流来包装输出流，再采用数据输入/输出输出流进行包装，加快传输的速度。废话少说，先来看服务器端的程序。

1.服务器端

package sterning;

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.net.ServerSocket;
import java.net.Socket;

public
class ServerTest
{
   
int port =
8821;

   
void start()
{
        Socket s
= null;
       
try {
            ServerSocket ss
= new ServerSocket(port);
           
while (true)
{
               
// 选择进行传输的文件
                String filePath
= "D:\\lib.rar";
                File fi
= new File(filePath);

                System.out.println("文件长度:"
+ (int) fi.length());

               
// public Socket accept() throws
               
// IOException侦听并接受到此套接字的连接。此方法在进行连接之前一直阻塞。

                s
= ss.accept();
                System.out.println("建立socket链接");
                DataInputStream dis
= new DataInputStream(new BufferedInputStream(s.getInputStream()));
                dis.readByte();

                DataInputStream fis
= new DataInputStream(new BufferedInputStream(new
FileInputStream(filePath)));
                DataOutputStream ps
= new DataOutputStream(s.getOutputStream());
               
//将文件名及长度传给客户端。这里要真正适用所有平台，例如中文名的处理，还需要加工，具体可以参见Think In Java 4th里有现成的代码。
                ps.writeUTF(fi.getName());
                ps.flush();
                ps.writeLong((long) fi.length());
                ps.flush();

               
int bufferSize
= 8192;
               
byte[] buf
= new
byte[bufferSize];

               
while (true)
{
                   
int read
= 0;
                   
if (fis
!= null)
{
                        read
= fis.read(buf);
                    }

                   
if (read
== -1)
{
                       
break;
                    }
                    ps.write(buf,
0, read);
                }
                ps.flush();
               
// 注意关闭socket链接哦，不然客户端会等待server的数据过来，
               
// 直到socket超时，导致数据不完整。               

                fis.close();
                s.close();               

                System.out.println("文件传输完成");
            }

       
} catch (Exception e)
{
            e.printStackTrace();
        }
    }

   
public
static void main(String arg[])
{
       
new ServerTest().start();
    }
}

2.socket的Util辅助类

package sterning;

import java.net.*;
import java.io.*;

public
class ClientSocket
{
   
private String ip;

   
private int port;

   
private Socket socket
= null;

    DataOutputStream out
= null;

    DataInputStream getMessageStream
= null;

   
public ClientSocket(String ip,
int port)
{
       
this.ip = ip;
       
this.port = port;
    }

   
/** *//**
     * 创建socket连接
     *
     *
@throws Exception
     *             exception
    
*/
   
public
void CreateConnection()
throws Exception
{
       
try {
            socket
= new Socket(ip, port);
       
} catch (Exception e)
{
            e.printStackTrace();
           
if (socket
!= null)
                socket.close();
           
throw e;
       
} finally
{
        }
    }

   
public
void sendMessage(String sendMessage)
throws Exception
{
       
try {
            out
= new DataOutputStream(socket.getOutputStream());
           
if (sendMessage.equals("Windows"))
{
                out.writeByte(0x1);
                out.flush();
               
return;
            }
           
if (sendMessage.equals("Unix"))
{
                out.writeByte(0x2);
                out.flush();
               
return;
            }
           
if (sendMessage.equals("Linux"))
{
                out.writeByte(0x3);
                out.flush();
           
} else
{
                out.writeUTF(sendMessage);
                out.flush();
            }
       
} catch (Exception e)
{
            e.printStackTrace();
           
if (out
!= null)
                out.close();
           
throw e;
       
} finally
{
        }
    }

   
public DataInputStream getMessageStream()
throws Exception
{
       
try {
            getMessageStream
= new DataInputStream(new BufferedInputStream(socket.getInputStream()));
           
return getMessageStream;
       
} catch (Exception e)
{
            e.printStackTrace();
           
if (getMessageStream
!= null)
                getMessageStream.close();
           
throw e;
       
} finally
{
        }
    }

   
public
void shutDownConnection()
{
       
try {
           
if (out
!= null)
                out.close();
           
if (getMessageStream
!= null)
                getMessageStream.close();
           
if (socket
!= null)
                socket.close();
       
} catch (Exception e)
{

        }
    }
}

3.客户端

package sterning;

import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileOutputStream;

public
class ClientTest
{
   
private ClientSocket cs
= null;

   
private String ip
= "localhost";//
设置成服务器IP

   
private int port
= 8821;

   
private String sendMessage
= "Windwos";

   
public ClientTest()
{
       
try {
           
if (createConnection())
{
                sendMessage();
                getMessage();
            }

       
} catch (Exception ex)
{
            ex.printStackTrace();
        }
    }

   
private
boolean createConnection()
{
        cs
= new ClientSocket(ip, port);
       
try {
            cs.CreateConnection();
            System.out.print("连接服务器成功!"
+ "\n");
           
return
true;
       
} catch (Exception e)
{
            System.out.print("连接服务器失败!"
+ "\n");
           
return
false;
        }

    }

   
private
void sendMessage()
{
       
if (cs ==
null)
           
return;
       
try {
            cs.sendMessage(sendMessage);
       
} catch (Exception e)
{
            System.out.print("发送消息失败!"
+ "\n");
        }
    }

   
private
void getMessage()
{
       
if (cs ==
null)
           
return;
        DataInputStream inputStream
= null;
       
try {
            inputStream
= cs.getMessageStream();
       
} catch (Exception e)
{
            System.out.print("接收消息缓存错误\n");
           
return;
        }

       
try {
           
//本地保存路径，文件名会自动从服务器端继承而来。
            String savePath
= "E:\\";
           
int bufferSize
= 8192;
           
byte[] buf
= new
byte[bufferSize];
           
int passedlen
= 0;
           
long len=0;
           

            savePath
+= inputStream.readUTF();
            DataOutputStream fileOut
= new DataOutputStream(new BufferedOutputStream(new
BufferedOutputStream(new FileOutputStream(savePath))));
            len
= inputStream.readLong();
           

            System.out.println("文件的长度为:"
+ len
+ "\n");
            System.out.println("开始接收文件!"
+ "\n");
                   

           
while (true)
{
               
int read
= 0;
               
if (inputStream
!= null)
{
                    read
= inputStream.read(buf);
                }
                passedlen
+= read;
               
if (read
== -1)
{
                   
break;
                }
               
//下面进度条本为图形界面的prograssBar做的，这里如果是打文件，可能会重复打印出一些相同的百分比
                System.out.println("文件接收了"
+  (passedlen
* 100/ len)
+ "%\n");
                fileOut.write(buf,
0, read);
            }
            System.out.println("接收完成，文件存为"
+ savePath
+ "\n");

            fileOut.close();
       
} catch (Exception e)
{
            System.out.println("接收消息错误"
+ "\n");
           
return;
        }
    }

   
public
static void main(String arg[])
{
       
new ClientTest();
    }
}

这就实现了从服务器端向客户端发送文件的过程,当然,反过来,也一样.稍有不同.代码中对跨平台的细节没有实现,有时间或兴趣的朋友可以提供一下.