Java 套接字自动通信

Question

服务器和客户端之间的通信有问题。我正在尝试找出一种自动通信方式，因为它们必须交换一些参数。但是，使用我编写的代码，服务器要么在客户端确认消息后继续向客户端发送相同的消息，要么客户端什么也没收到。插座和所有内容之前都已设置好。函数 sendString(( 和 receiveString(( 在两个代码示例中是相同的。有没有正确的方法可以做到这一点？我不明白为什么这不起作用...

服务器：

String buffer;
while(true){
buffer = client.receiveString();
if(buffer != null && buffer.equals("ready")){
System.out.println("Client is ready");
client.sendString("ready");
while(true){
buffer = client.receiveString();
if(buffer != null && buffer.equals("k")){
System.out.println("stopped");
break;
}
}
break;
}
}
public String receiveString() throws IOException{         //From the client class
if(dataIn.available() > 0){
int length = dataIn.readInt();
byte[] b = new byte[length];
dataIn.readFully(b, 0, b.length);
return new String(b, Charset.forName("UTF-8"));
}
return null;
}
public void sendString(String msg) throws IOException{
byte[] b = msg.getBytes(Charset.forName("UTF-8"));
dataOut.writeInt(b.length);
dataOut.write(b);
}

客户：

String buffer;
while(true){
sendString("ready");
buffer = receiveString();
if(buffer!=null)
System.out.println(buffer);
if(buffer != null && buffer.equals("ready")){   
System.out.println("Server is ready");
sendString("k");
break;
}
}

Answer 1

此代码可能适用于您的情况：

客户端.java

public class Client {
public static void main(String[] args) throws Exception {
try (Socket socket = new Socket("localhost", 8080)) {
try (BufferedOutputStream out = new BufferedOutputStream(socket.getOutputStream());
Scanner in = new Scanner(socket.getInputStream())) {
System.out.println("Client: sending ready.");
writeLine("ready", out);
System.out.println("Client: sent ready.");
String line = in.nextLine();
if ("ready".equals(line)) {
System.out.println("Client: server is ready");
writeLine("k", out);
}
}
}
}
private static void writeLine(final String line, final BufferedOutputStream out) throws IOException {
out.write((line +"n").getBytes());
out.flush();
}
}

服务器.java：

public class Server {
public static void main(String[] args) throws Exception {
boolean running = true;
try (ServerSocket socket = new ServerSocket(8080, 0)) {
while (running) {
System.out.println("Waiting for client accept.");
try (final Socket client = socket.accept();
final Scanner in = new Scanner(client.getInputStream());
final BufferedOutputStream out = new BufferedOutputStream(client.getOutputStream())) {
System.out.println("Waiting for client ready.");
String line = readLine(in);
if ("ready".equals(line)) {
writeLine("ready", out);
while (running) {
line = readLine(in);
if (line != null && line.equals("k")) {
System.out.println("Server: received stop signal");
running = false;
} else {
Thread.sleep(100);
System.out.println("Server: waiting for command.");
}
}
}
}
}
}
}
private static String readLine(final Scanner in) {
String line = in.nextLine();
System.out.println("Server: client sent " + line);
return line;
}
private static void writeLine(final String line, final BufferedOutputStream out) throws IOException {
out.write((line + "n").getBytes());
out.flush();
}
}

那么这里发生了什么？ 服务器套接字等待客户端。如果客户端连接，它会等待它发送一些东西(以阻止的方式！如果它"就绪"，它会检查其他命令。

注意：这一次仅适用于单个服务器<>客户端连接。不知道这是否适合您的应用程序。如果客户端发送"k"，服务器将关闭，就像您的情况一样。