项目须要是通过WIFI建立手机和PC的通信，然后自己定义一个简单的协议对要传输的文件进行校验，传输的文件是2张3M的图片，要求考虑网络中断情况处理。
我这里採用的是非堵塞socket来实现的，之前查过非常多资料，认为这样的比較方便，其有用传统的那种socket也是能够实现的，至于堵塞问题，能够开两个线程。这样保证读取不是同一个线程，也就能够解决。
程序大致是这种流程，手机端发送一个“filename”字符串给PC，PC校验字符串后返回文件名称。然后手机端再把接收到的文件名称发送给PC端。进行校验，假设PC端校验成功，那么PC端就開始传输这个文件给手机端。手机端就接收这个文件。
至于网络中断的问题，后来发现，仅仅要在服务端发送文件的那一段程序加入try-catch，捕获这个异常，这样服务端的程序就不会死掉，进入等待。等到手机再次和PC端建立连接。那么就能够又一次发送文件。这里是重传，而不是续传，后来想过。也仅仅有6M，实际測试过。大概2-3秒就能够传完。重传和续传意义不大，所以就简单的重传了。
程序例如以下：
PC端：
public class MyServer {
private final static Logger logger = Logger.getLogger(MyServer.class.getName());
public static void main(String[] args) {
Selector selector = null;
ServerSocketChannel serverSocketChannel = null;
try {
selector = Selector.open();
serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.configureBlocking(false);
serverSocketChannel.socket().setReuseAddress(true);
serverSocketChannel.socket().bind(new InetSocketAddress(1991));
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
while (selector.select() > 0) {
Iterator<SelectionKey> it = selector.selectedKeys().iterator();
while (it.hasNext()) {
SelectionKey readyKey = it.next();
it.remove();
SocketChannel socketChannel = null;
String string = "";
try {
socketChannel = ((ServerSocketChannel) readyKey.channel()).accept();
string = receiveData(socketChannel);
logger.log(Level.INFO, string);
if(string.equals("filename")){
File f= new File("D:/chz.jpg");
if (f.exists() && f.isFile()){
sendData(socketChannel, "chz.jpg");
}else{
logger.info("file doesn't exist or is not a file");
}
}
if(string.equals("chz.jpg")){
sendFile(socketChannel, new File("D:/chz.jpg"));
}
}catch(Exception ex){
logger.log(Level.SEVERE, "1", ex);
} finally {
try {
socketChannel.close();
} catch(Exception ex) {
logger.log(Level.SEVERE, "2", ex);
}
}
}
}
} catch (ClosedChannelException ex) {
logger.log(Level.SEVERE, "3", ex);
} catch (IOException ex) {
logger.log(Level.SEVERE, "4", ex);
} finally {
try {
selector.close();
} catch(Exception ex) {
logger.log(Level.SEVERE, "5", ex);
}
try {
serverSocketChannel.close();
} catch(Exception ex) {
logger.log(Level.SEVERE, "6", ex);
}
}
}
private static String receiveData(SocketChannel socketChannel) throws IOException {
String string = null;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ByteBuffer buffer = ByteBuffer.allocate(1024);
try {
byte[] bytes;
int size = 0;
while ((size = socketChannel.read(buffer)) >= 0) {
buffer.flip();
bytes = new byte[size];
buffer.get(bytes);
baos.write(bytes);
buffer.clear();
}
bytes = baos.toByteArray();
string = new String(bytes);
}catch(Exception ex){
logger.log(Level.SEVERE, "7", ex);
}finally {
try {
baos.close();
} catch(Exception ex) {
logger.log(Level.SEVERE, "8", ex);
}
}
return string;
}
private static void sendData(SocketChannel socketChannel, String string) throws IOException {
byte[] bytes = string.getBytes();
ByteBuffer buffer = ByteBuffer.wrap(bytes);
socketChannel.write(buffer);
socketChannel.socket().shutdownOutput();
}
private static void receiveFile(SocketChannel socketChannel, File file) throws IOException {
FileOutputStream fos = null;
FileChannel channel = null;
try {
fos = new FileOutputStream(file);
channel = fos.getChannel();
ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
int size = 0;
while ((size = socketChannel.read(buffer)) != -1) {
buffer.flip();
if (size > 0) {
buffer.limit(size);
channel.write(buffer);
buffer.clear();
}
}
}catch(Exception ex){
logger.log(Level.SEVERE, "9", ex);
} finally {
try {
channel.close();
} catch(Exception ex) {
logger.log(Level.SEVERE, "10", ex);
}
try {
fos.close();
} catch(Exception ex) {
logger.log(Level.SEVERE, "11", ex);
}
}
}
private static void sendFile(SocketChannel socketChannel, File file) throws IOException {
FileInputStream fis = null;
FileChannel channel = null;
try {
fis = new FileInputStream(file);
channel = fis.getChannel();
ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
int size = 0;
while ((size = channel.read(buffer)) != -1) {
buffer.rewind();
buffer.limit(size);
socketChannel.write(buffer);
buffer.clear();
}
socketChannel.socket().shutdownOutput();
}catch(Exception ex){
logger.log(Level.SEVERE, "12", ex);
} finally {
try {
channel.close();
} catch(Exception ex) {
logger.log(Level.SEVERE, "13", ex);
}
try {
fis.close();
} catch(Exception ex) {
logger.log(Level.SEVERE, "14", ex);
}
}
}
}
ANDROID端：
public class MainActivity extends Activity {
private Button mButton;
private EditText et;
private static String string;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
et = (EditText)findViewById(R.id.edittext1);
et.setText("192.168.1.214");
mButton = (Button)findViewById(R.id.button1);
mButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
string = et.getText().toString();
new Thread(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
SocketChannel socketChannel = null;
try {
socketChannel = SocketChannel.open();
SocketAddress socketAddress = new InetSocketAddress(string, 1991);
socketChannel.connect(socketAddress);
sendData(socketChannel, "filename");
String string = "";
string = receiveData(socketChannel);
if(!string.isEmpty()){
socketChannel = SocketChannel.open();
socketChannel.connect(new InetSocketAddress("192.168.1.214", 1991));
sendData(socketChannel, string);
receiveFile(socketChannel, new File("sdcard/afile/"+string));
}
} catch (Exception ex) {
Log.i("chz", null, ex);
} finally {
try {
socketChannel.close();
} catch(Exception ex) {}
}
}
}).start();
}
});
}
private void sendData(SocketChannel socketChannel, String string) throws IOException {
byte[] bytes = string.getBytes();
ByteBuffer buffer = ByteBuffer.wrap(bytes);
socketChannel.write(buffer);
socketChannel.socket().shutdownOutput();
}
private String receiveData(SocketChannel socketChannel) throws IOException {
String string = null;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
byte[] bytes;
int count = 0;
while ((count = socketChannel.read(buffer)) >= 0) {
buffer.flip();
bytes = new byte[count];
buffer.get(bytes);
baos.write(bytes);
buffer.clear();
}
bytes = baos.toByteArray();
string = new String(bytes);
// socketChannel.socket().shutdownInput();
} finally {
try {
baos.close();
} catch(Exception ex) {}
}
return string;
}
private static void sendFile(SocketChannel socketChannel, File file) throws IOException {
FileInputStream fis = null;
FileChannel channel = null;
try {
fis = new FileInputStream(file);
channel = fis.getChannel();
ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
int size = 0;
while ((size = channel.read(buffer)) != -1) {
buffer.rewind();
buffer.limit(size);
socketChannel.write(buffer);
buffer.clear();
}
socketChannel.socket().shutdownOutput();
} finally {
try {
channel.close();
} catch(Exception ex) {}
try {
fis.close();
} catch(Exception ex) {}
}
}
private static void receiveFile(SocketChannel socketChannel, File file) throws IOException {
FileOutputStream fos = null;
FileChannel channel = null;
try {
fos = new FileOutputStream(file);
channel = fos.getChannel();
ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
int size = 0;
while ((size = socketChannel.read(buffer)) != -1) {
buffer.flip();
if (size > 0) {
buffer.limit(size);
channel.write(buffer);
buffer.clear();
}
}
} finally {
try {
channel.close();
} catch(Exception ex) {}
try {
fos.close();
} catch(Exception ex) {}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
番外：事实上做这个文件传输遇到的最头痛的问题不是程序难不难写。而是wifi通信的建立。最初我是用自己win7的电脑连路由器。然后手机也连路由器做的測试，没有问题。但是后来项目需求是下位机是一台XP的电脑。并且要求点对点建立wifi，所以仅仅能有一端设成wifi热点。还有一端连接这个热点。设想非常完美，然后找了实验室唯一一台XP电脑測试了两天，都没有可以让我手机连上PC。后来各种问，才知道XP不支持为android创wifi热点，真心坑呀。然后我就想反过来做呗，手机建wifi热点，电脑连。耶果然连上了，但是。明明写好的程序，各种执行不了，最后手机巨热，（我心痛死我的小米。求不黑小米。真心一直用小米，仅仅是导师不给配开发手机，仅仅能用自己手机，哎）所以直接pass这个想法，最后百度了一下。貌似可以接外接硬件设备，例如说360随身wifi硬件，嗯导师最终答应淘宝买一个来測试下，今天买吧。
哦，整个程序參考了两位大神博客：http://www.cnblogs.com/hongten/archive/2012/04/29/java_socket.html
http://blog.csdn.net/kongxx/article/details/7288896尤其是后面这位大神的一个专栏专门讲java socket的。讲得非常好。
这个文件传输的整个project地址：http://download.csdn.net/detail/u012321815/8047863