我正在开发一个需要 TCP 客户端和服务器的项目，其中服务器将消息回显给客户端。以下来自作业：
服务器应用程序应：
- 侦听已知 IP 地址和端口上的 TCP 连接
- 接受在该端口上发起的连接
- 接收来自客户端的消息并回显它们
- 继续这样做，直到客户端断开连接。
客户端应用程序应：
- 在其众所周知的 IP 地址和端口上与服务器建立连接
- 以异步方式向服务器发送消息。消息的格式由您选择；但是，它必须包含足够的信息才能在从服务器返回时被识别。
我已经完成了服务器的编码，这就是我为客户提出的。
我的问题：
服务器在众所周知的 IP 和端口上侦听 TCP 连接是什么意思 在我的实现中，我使用
ServerSocket了接受服务器侦听的端口。我解释正确了吗？在我当前的 TCPClient 实现中，客户端向服务器发送消息，但 println() 似乎是一个阻塞调用，这使得它是同步的。我该怎么做才能使我的客户端异步？
为简洁起见，我没有添加TCPServer的代码，如果需要请告诉我
更新* * 根据反馈，我已通过 TCPClient 类进行了修改。收到客户端请求后，我生成了两个线程 ReceiveMessage 和 SendMessage。这样做会给我以下异常：
[Client] Message sent: Message from Client 97
[Client] Message sent: Message from Client 98
[Client] Message sent: Message from Client 99
[Client] Done Sending all the messages
java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:264)
at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306)
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158)
at java.io.InputStreamReader.read(InputStreamReader.java:167)
at java.io.BufferedReader.fill(BufferedReader.java:136)
at java.io.BufferedReader.readLine(BufferedReader.java:299)
at java.io.BufferedReader.readLine(BufferedReader.java:362)
at org.chanders.client.ReceiveMessage.run(ReceiveMessage.java:18)
at java.lang.Thread.run(Thread.java:680)
以下是新的客户代码：
public class TCPClient {
Socket clientSocket = null;
OutputStream out = null;
BufferedReader in = null;
String message = "Hello from Client";
int messagecount = 100;
// server credentials
private static final String SERVER_ADDRESS = "localhost";
private static final int SERVER_PORT = 50001;
protected void execute() {
try {
clientSocket = new Socket(SERVER_ADDRESS, SERVER_PORT);
Thread send = new Thread(new SendMessage(clientSocket.getOutputStream()));
Thread receive = new Thread(new ReceiveMessage(clientSocket.getInputStream()));
send.start();
receive.start();
//For server to wait until send and receive threads finish
send.join();
receive.join();
} catch (UnknownHostException uhe) {
System.err.println("Couldnt find host: " + SERVER_ADDRESS);
uhe.printStackTrace();
System.exit(-1);
}catch(IOException ioe) {
System.err.println("Couldnt get I/O: " + SERVER_ADDRESS);
ioe.printStackTrace();
System.exit(-1);
}catch(InterruptedException ie) {
System.err.println("Thread.join failed: ");
ie.printStackTrace();
System.exit(-1);
}
finally {
//cleanup();
}
}
private void cleanup() {
try {
clientSocket.close();
}catch(Exception e) {
e.printStackTrace();
System.exit(-1);
}
}
public static void main(String[] args) {
TCPClient client = new TCPClient();
client.execute();
}
public class SendMessage implements Runnable {
OutputStream out = null;
String message = "Message from Client";
int messageCount = 100;
public SendMessage(OutputStream out) {
this.out = out;
}
public void run() {
PrintWriter writer = new PrintWriter(out);
try {
for (int i = 0; i < messageCount; i++) {
String m = message + " " + i;
writer.println(m);
System.out.println("[Client] Message sent: " + m);
}
System.out.println("[Client] Done Sending all the messages");
} catch (Exception e) {
e.printStackTrace();
System.exit(-1);
} finally {
cleanup();
}
}
private void cleanup() {
try {
out.close();
}catch(Exception e) {
e.printStackTrace();
System.exit(-1);
}
}
}
public class ReceiveMessage implements Runnable {
InputStream in = null;
String message;
public ReceiveMessage(InputStream in) {
this.in = in;
}
public void run() {
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
try {
while ((message = reader.readLine()) != null) {
System.out.println("[Client] Received message from Server: "
+ message);
}
System.out.println("[Client] Done Receiving messages from Server");
} catch (Exception e) {
e.printStackTrace();
} finally {
cleanup();
}
}
private void cleanup() {
try {
in.close();
}catch(Exception e) {
e.printStackTrace();
System.exit(-1);
}
}
}