用於客戶端從伺服器端下載檔案

伺服器（Server）

package com.socket.sample;

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) {
				// 選擇進行傳輸的檔案
				String filePath = "D:\\lib.rar";
				File fi = new File(filePath);

				System.out.println("檔案長度:" + (int) fi.length());

				// public Socket accept() throws
				// IOException偵聽並接受到此套接字的連線。此方法在進行連線之前一直阻塞。

				s = ss.accept();
				System.out.println("建立socket連結");
				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());
				// 將檔名及長度傳給客戶端。這裡要真正適用所有平臺，例如中文名的處理，還需要加工，具體可以參見Think In Java
				// 4th裡有現成的程式碼。
				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);
						// 從包含的輸入流中讀取一定數量的位元組，並將它們儲存到緩衝區陣列 b
						// 中。以整數形式返回實際讀取的位元組數。在輸入資料可用、檢測到檔案末尾 (end of file)
						// 或丟擲異常之前，此方法將一直阻塞。
					}

					if (read == -1) {
						break;
					}
					ps.write(buf, 0, read);
				}
				ps.flush();
				// 注意關閉socket連結哦，不然客戶端會等待server的資料過來，
				// 直到socket超時，導致資料不完整。
				fis.close();
				s.close();
				System.out.println("檔案傳輸完成");
			}

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

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

客戶端工具（SocketTool）

package com.socket.sample;

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.Socket;

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;
	}

	/** */
	/**
	 * 建立socket連線
	 * 
	 * @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) {

		}
	}
}
 

客戶端（Client）

package com.socket.sample;

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";// 設定成伺服器IP

	private int port = 8821;

	private String sendMessage = "Windows";

	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("連線伺服器成功!" + "\n");
			return true;
		} catch (Exception e) {
			System.out.print("連線伺服器失敗!" + "\n");
			return false;
		}

	}

	private void sendMessage() {
		if (cs == null)
			return;
		try {
			cs.sendMessage(sendMessage);
		} catch (Exception e) {
			System.out.print("傳送訊息失敗!" + "\n");
		}
	}

	private void getMessage() {
		if (cs == null)
			return;
		DataInputStream inputStream = null;
		try {
			inputStream = cs.getMessageStream();
		} catch (Exception e) {
			System.out.print("接收訊息快取錯誤\n");
			return;
		}

		try {
			// 本地儲存路徑，檔名會自動從伺服器端繼承而來。
			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 FileOutputStream(savePath)));
			len = inputStream.readLong();

			System.out.println("檔案的長度為:" + len + "\n");
			System.out.println("開始接收檔案!" + "\n");

			while (true) {
				int read = 0;
				if (inputStream != null) {
					read = inputStream.read(buf);
				}
				passedlen += read;
				if (read == -1) {
					break;
				}
				// 下面進度條本為圖形介面的prograssBar做的，這裡如果是打檔案，可能會重複打印出一些相同的百分比
				System.out.println("檔案接收了" + (passedlen * 100 / len) + "%\n");
				fileOut.write(buf, 0, read);
			}
			System.out.println("接收完成，檔案存為" + savePath + "\n");

			fileOut.close();
		} catch (Exception e) {
			System.out.println("接收訊息錯誤" + "\n");
			return;
		}
	}

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

測試是成功的，在DOS命令列下編譯~~~