Java 使用套接字打印原始文本

我正在开发一个应用程序，可以打印到我当地的wifi打印机上，但超过9100个端口我没有响应，超过515个端口我“连接被拒绝”

代码如下：

Socket test = new Socket();
Socket sock = new Socket(ip,9100);
PrintWriter oStream = new PrintWriter(sock.getOutputStream());

oStream.printf("========================\n");
oStream.printf("PROVA STAMPA\n");
oStream.printf("HELLO SLOW SUD\n");
oStream.printf("========================"+"\n");

oStream.close();
sock.close();

我也尝试过这个：

Socket objSocket = new Socket();

InetSocketAddress objEndPoint = new InetSocketAddress(ip, 9100);

DataOutputStream objOutputStream;

objSocket.connect(objEndPoint, 6000);

objOutputStream = new DataOutputStream(objSocket.getOutputStream());
objOutputStream.write(("========================\nPROVA STAMPA\nHELLO SLOW SUD\n========================\n").getBytes());

objOutputStream.close();
objSocket.close();

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哪行代码失败了？我不知道，只是打印机没有发送响应