[英]inputstream.available() is 0 always
我不知道我的代碼發生了什么。 我沒有收到任何錯誤,也沒有回應。 我正在將數據寫入串行端口並通過激活port.notifyOnDataAvailable(true);
但是這個事件沒有被觸發並且 inputstream.available() 總是返回 0。 可能有什么問題? 我在 linux 中使用 RXTX。
編輯
package testConn;
import forms_helper.global_variables;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.UnsupportedEncodingException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.comm.*;
import java.util.*;
/** Check each port to see if it is open. **/
public class openPort implements SerialPortEventListener {
static Enumeration portList;
static CommPortIdentifier portId;
static String messageString;
public static SerialPort serialPort;
static OutputStream outputStream;
InputStream inputStream;
static boolean outputBufferEmptyFlag = false;
private BufferedReader is;
private PrintStream os;
public void open() {
Enumeration port_list = CommPortIdentifier.getPortIdentifiers();
while (port_list.hasMoreElements()) {
// Get the list of ports
CommPortIdentifier port_id = (CommPortIdentifier) port_list.nextElement();
if (port_id.getName().equals("/dev/ttyS1")) {
// Attempt to open it
try {
SerialPort port = (SerialPort) port_id.open("PortListOpen", 20000);
System.out.println("Opened successfully:"+port);
try {
int baudRate = 9600; //
port.setSerialPortParams(
baudRate,
SerialPort.DATABITS_7,
SerialPort.STOPBITS_1,
SerialPort.PARITY_EVEN);
port.setDTR(true);
port.setFlowControlMode(SerialPort.FLOWCONTROL_NONE);
System.out.println("properties are set");
} catch (UnsupportedCommOperationException e) {
System.out.println(e);
}
try {
//input = new SerialReader(in);
port.addEventListener(this);
System.out.println("listeners attached" + this);
} catch (TooManyListenersException e) {
System.out.println("too many listeners");
}
port.notifyOnDataAvailable(true);
//port.notifyOnOutputEmpty(true);
//sendMessage(port,"@PL");
//port.close ();
try {
is = new BufferedReader(new InputStreamReader(port.getInputStream()));
} catch (IOException e) {
System.err.println("Can't open input stream: write-only");
is = null;
}
try {
os = new PrintStream(port.getOutputStream(), true);
} catch (IOException ex) {
Logger.getLogger(openPort.class.getName()).log(Level.SEVERE, null, ex);
}
try {
inputStream = port.getInputStream();
System.out.println("inputstream" + inputStream.available());
outputStream = (OutputStream) port.getOutputStream();
os = new PrintStream(port.getOutputStream(), true, "US-ASCII");
} catch (IOException e) {
System.out.println(e);
}
//set the created variables to global variables
global_variables.port = port;
global_variables.inputStream = inputStream;
System.out.println(inputStream);
System.out.println(outputStream);
global_variables.outputStream = outputStream;
global_variables.os = os;
} catch (PortInUseException pe) {
System.out.println("Open failed");
String owner_name = port_id.getCurrentOwner();
if (owner_name == null) {
System.out.println("Port Owned by unidentified app");
} else // The owner name not returned correctly unless it is
// a Java program.
{
System.out.println(" " + owner_name);
}
}
}
}
}
public static void sendMessage(SerialPort port, String msg) {
if (port != null) {
System.out.println(msg);
try {
byte[] bytes = msg.getBytes("US-ASCII");
try {
global_variables.outputStream.write(bytes);
System.out.println(bytes.length);
global_variables.outputStream.flush();
} catch (IOException ex) {
Logger.getLogger(openPort.class.getName()).log(Level.SEVERE, null, ex);
}
} catch (UnsupportedEncodingException ex) {
Logger.getLogger(openPort.class.getName()).log(Level.SEVERE, null, ex);
}
System.out.println("Opened successfully:"+msg.getBytes());
//global_variables.outputStream.write(msg.getBytes());
//global_variables.outputStream.flush();
//global_variables.os.print(msg);
System.out.println(global_variables.outputStream);
try {
Thread.sleep(2000); // Be sure data is xferred before closing
System.out.println("read called");
//SimpleRead read = new SimpleRead();
//int read = global_variables.inputStream.read();
//System.out.println("read call ended"+read);
} catch (Exception e) {
}
}
}
public void serialEvent(SerialPortEvent event) {
System.out.println(event.getEventType());
String line;
try {
line = is.readLine();
if (line == null) {
System.out.println("EOF on serial port.");
System.exit(0);
}
os.println(line);
} catch (IOException ex) {
System.err.println("IO Error " + ex);
}
switch (event.getEventType()) {
/*
case SerialPortEvent.BI:
case SerialPortEvent.OE:
case SerialPortEvent.FE:
case SerialPortEvent.PE:
case SerialPortEvent.CD:
case SerialPortEvent.CTS:
case SerialPortEvent.DSR:
case SerialPortEvent.RI:
case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
System.out.println("event.getEventType()");
break;
*
*/
case SerialPortEvent.DATA_AVAILABLE:
System.out.println("inside event handler data available");
byte[] readBuffer = new byte[20];
try {
while (inputStream.available() > 0) {
int numBytes = inputStream.read(readBuffer);
}
System.out.print(new String(readBuffer));
System.exit(1);
} catch (IOException e) {
System.out.println(e);
}
break;
}
}
} // PortListOpen
我在 main 方法上打開端口並在應用程序內的按鈕單擊事件上發送消息。
.available()
不能用於進程間通信(包括串行),因為它只檢查當前進程中是否有可用數據(在輸入緩沖區中)。
在串行通信中,當您發送一條消息然后立即調用available()
時,您通常會得到 0,因為串行端口尚未回復任何數據。
解決方案是在單獨的線程中使用阻塞read()
(使用interrupt()
來結束它):
部分回答您的問題。
來自 javadocs
class InputStream 的可用方法始終返回 0。
http://download.oracle.com/javase/6/docs/api/java/io/InputStream.html#available ()
所以那部分至少和預期的一樣
通過使用 PrintStream,您可以抑制在任何請求/響應場景中需要了解的異常。
很可能你還沒有發送任何東西。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.