import java.net. *; import java.io. *; public class EchoClient{ public static void main(String args[]){ try{ Socket connection = new Socket(args[0], 7); System.out.println("Connection established:"); DataInputStream in = new DataInputStream( connection.getInputStream()); DataOutputStream out = new DataOutputStream( connection.getoutputStream()); String line = new String(""); while(!line.toUpperCase().equals(".QUIT")){ System.out.print("Enter string: "); line = readString(); System.out.println("\tSending string to server... "); out.writeUTF(line); System.out.println("\tWaiting for server response... "); line = in.readUTF(); System.out.println("Received: " + line);} in.close(); out.close(); connection.close(); } catch(UnknownHostException uhe){ System.err.println("Unknon host: " + args[0]); } catch(IOException ioe) { System.err.println("IOException: " + ioe); } } public static String readString(){ String string = new String(); BufferedReader in = new BufferedReader(new InputStreamReader(System.in)); try{ string = in.readLine(); }catch(IOException e){ System. out. println("Console. readString: Unknon error..."); System.exit(-1); } return string;} }哪里错了

代码有一个小写字母错误，它导致了编译错误。第16行中的 `connection.getoutputStream()` 应该改为 `connection.getOutputStream()`。将该行代码更改为以下代码将解决问题：

DataOutputStream out = new DataOutputStream(connection.getOutputStream());

除此之外，还有一些其他的小问题：

1. 在 `String` 对象初始化时，最好使用 `""` 而不是 `new String()`。
2. 在 `catch` 语句中，应该使用 `System.out.println()` 而不是 `System. out. println()`。
3. 在 `readString()` 方法中，有一个拼写错误，应该是 "unknown" 而不是 "unknon"。
4. 最后，建议在 `catch` 块中输出详细的错误信息，以便更好地调试问题。

修改后的代码如下所示：

import java.net.*;
import java.io.*;

public class EchoClient {
    public static void main(String args[]) {
        try {
            Socket connection = new Socket(args[0], 7);
            System.out.println("Connection established:");
            DataInputStream in = new DataInputStream(connection.getInputStream());
            DataOutputStream out = new DataOutputStream(connection.getOutputStream());
            String line = "";
            while (!line.toUpperCase().equals(".QUIT")) {
                System.out.print("Enter string: ");
                line = readString();
                System.out.println("\tSending string to server... ");
                out.writeUTF(line);
                System.out.println("\tWaiting for server response... ");
                line = in.readUTF();
                System.out.println("Received: " + line);
            }
            in.close();
            out.close();
            connection.close();
        } catch (UnknownHostException uhe) {
            System.err.println("Unknown host: " + args[0]);
        } catch (IOException ioe) {
            System.err.println("IOException: " + ioe.getMessage());
        }
    }

    public static String readString() {
        String string = "";
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        try {
            string = in.readLine();
        } catch (IOException e) {
            System.err.println("Console.readString: Unknown error...");
            System.exit(-1);
        }
        return string;
    }
}

希望这可以帮助您解决问题！