創建阻塞的 EchoClient
客戶程式一般不需要同時建立與服務器的多個連接，因此用一個執行緒，按照阻塞模式運行就能滿足需求
public class EchoClient {
private SocketChannel socketChannel = null;
public EchoClient() throws IOException {
socketChannel = SocketChannel.open();
InetAddress ia = InetAddress,getLocalHost();
InetSocketAddress isa = new InetSocketAddress(ia,8000);
socketChannel.connect(isa); //連接服務器
}
public static void main(String args[])throws IOException {
new EchoClient().talk();
}
private PrintWriter getWriter(Socket socket) throws IOException {
OutputStream socketOut = socket.getOutputStream();
return new PrintWriter(socketOut,true);
}
private BufferedReader getReader(Socket socket) throws IOException {
InputStream socketIn = socket.getInputStream();
return new BufferedReader(new InputStreamReader(socketIn));
}
public void talk() throws IOException {
try {
BufferedReader br = getReader(socketChannel.socket());
PrintWriter pw = getWriter(socketChannel.socket());
BufferedReader localReader = new BufferedReader(new InputStreamReader(System.in));
String msq = null;
while((msg = localReader.readLine()) != null) {
pw.println(msg);
System.out.println(br.readLine());
if(msq.equals("bye")) {
break;
}
}
} catch(IOException e) {
e.printStackTrace();
} finally {
try {
socketChannel.close();
} catch(IOException e) {
e.printStackTrace();
}
}
}
}
創建非阻塞的 EchoClient
對于客戶與服務器之間的通信，按照它們收發資料的協調程度來區分，可分為同步通信和異步通信
同步通信指甲方向乙方發送了一批資料后，必須等接收到了乙方的回應資料后，再發送下一批資料，同步通信要求一個 IO 操作完成之后，才能完成下一個 IO 操作，用阻塞模式更容易實作
異步通信指發送資料和接收資料的操作互不干擾，各自獨立進行，異步通信允許發送資料和接收資料的操作各自獨立進行，用非阻塞模式更容易實作
值得注意的是，通信的兩端并不要求都采用同樣的通信方式，當一方采用同步通信時，另一方可以采用異步通信
public class EchoClient {
private SocketChannel socketChannel = null;
private ByteBuffer sendBuffer = ByteBuffer.allocate(1024);
private ByteBuffer receiveBuffer = ByteBuffer.allocate(1024);
private Charset charset = Charset.forName("GBK");
private Selector selector;
public EchoClient() throws IOException {
socketChannel = SocketChannel.open();
InetAddress ia = InetAddress.getLocalHost();
InetSocketAddress isa = new InetSocketAddress(ia, 8000);
socketChannel.connect(isa); //采用阻塞模式連接服務器
socketChannel.configureBlocking(false); //設定為非阻塞模式
selector = Selector.open();
}
public static void main(String args[]) throws IOException {
final EchoClient client = new EchoClient();
Thread receiver=new Thread() {
public void run() {
client.receiveFromUser(); //接收用戶向控制臺輸入的資料
}
};
receiver.start();
client.talk();
}
/** 接收用戶從控制臺輸入的資料，放到sendBuffer中 */
public void receiveFromUser() {
try {
BufferedReader localReader = new BufferedReader(new InputStreamReader(System.in));
String msg = null;
while((msg = localReader.readLine()) != null) {
synchronized(sendBuffer) {
sendBuffer.put(encode(msg + "\r\n"));
}
if (msg.equals("bye")) {
break;
}
}
} catch(IOException e) {
e.printStackTrace();
}
}
//接收和發送資料
public void talk() throws IOException {
socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE);
while (selector.select() > 0 ) {
Set readyKeys = selector.selectedKeys();
Iterator it = readyKeys.iterator();
while (it.hasNext()) {
SelectionKey key = null;
try {
key = (SelectionKey) it.next();
it.remove();
if (key.isReadable()) {
receive(key);
}
if (key.isWritable()) {
send(key);
}
} catch(IOException e) {
e.printStackTrace();
try {
if(key != null) {
key.cancel();
key.channel().close() ;
}
} catch(Exception ex) {
e.printStackTrace();
}
}
}
}
}
public void send(SelectionKey key) throws IOException {
//發送sendBuffer的資料
SocketChannel socketChannel = (SocketChannel)key.channel();
synchronized(sendBuffer) {
sendBuffer.flip(); //把極限設為位置，把位置設為0
socketChannel.write(sendBuffer); //發送資料
sendBuffer.compact(); //洗掉已經發送的資料
}
}
public void receive(SelectionKey key) throws IOException {
//接收EchoServer發送的資料，把它放到receiveBuffer
//如果receiveBuffer有一行資料，就列印這行資料，然后把它從receiveBuffer洗掉
SocketChannel socketChannel = (SocketChannel) key.channel();
socketChannel.read(receiveBuffer):
receiveBuffer.flip();
String receiveData = https://www.cnblogs.com/Yee-Q/archive/2023/05/20/decode (receiveBuffer);
if(receiveData.indexOf("\n") == -1) return;
String outputData = https://www.cnblogs.com/Yee-Q/archive/2023/05/20/receiveData.substring(0, receiveData.indexOf("\n") + 1):
System.out.print(outputData);
if(outputData.equals("echo:bye\r\n")) {
key.cancel():
socketChannel.close();
selector.close();
System.exit(0);
}
ByteBuffer temp = encode(outputData);
receiveBuffer.position(temp.limit());
receiveBuffer.compact(): //洗掉已經列印的資料
}
//解碼
public String decode(ByteBuffer buffer) {
CharBuffer charBuffer= charset.decode(buffer);
return charBuffer.toString();
}
//編碼
public ByteBuffer encode(String str) {
return charset.encode(str);
}
}
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