我正在制作一个 Java(版本控制)应用程序,其中客户端和服务器通过套接字流进行通信。我遇到的问题是客户端或服务器在执行 readline() 时往往会阻塞,最终导致另一端也阻塞。奇怪的是,第一次运行的时候好像没有出现这个错误。
我花了很多时间来找出导致问题的原因以及如何解决它,但我只能将我的问题强烈减少到下面提供的代码。 MAKE_STUB 参数允许使用管道流而不是套接字流。经常会导致线程在client读完之前就关闭导致的错误,但是有时候也会出现和使用sockets一样的错误,这大概说明问题不是socket的误用,而是stream的误用?
我还尝试了以下操作:更改刷新输出的时间,在 println() 中添加 +“\n”,依次发送/接收 (PING_PONG),防止流被垃圾收集(使用静态列表),发送一个字符串而不是 JSON 等。我觉得奇怪的是,这些解决方案只会导致 block 发生得更早或更晚。
客户端代码:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import java.io.PrintWriter;
import java.io.Writer;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.UnknownHostException;
public class TestClientProt {
private static final boolean MAKE_STUB = false;
private static final boolean PING_PONG = false;
private static void send(String value, InputStream rawInput, OutputStream rawOutput) throws IOException {
PrintWriter output = new PrintWriter(rawOutput);
output.println(value);
output.flush();
if(PING_PONG) {
BufferedReader input = new BufferedReader(new InputStreamReader(rawInput));
if(!input.readLine().equals(value))
System.err.println("Ping pong failed!");
}
}
private static int receiveInt(InputStream rawInput, OutputStream rawOutput) throws NumberFormatException, IOException {
return Integer.parseInt(receiveString(rawInput, rawOutput));
}
private static String receiveString(InputStream rawInput, OutputStream rawOutput) throws IOException {
BufferedReader input = new BufferedReader(new InputStreamReader(rawInput));
String value = input.readLine();
if(PING_PONG) {
PrintWriter output = new PrintWriter(rawOutput);
output.println(value);
output.flush();
}
return value;
}
public static void main(String[] args) throws IOException {
Socket socket;
InputStream rawInput;
OutputStream rawOutput;
if(MAKE_STUB) {
rawInput = new PipedInputStream();
final OutputStream rawServerOutput = new PipedOutputStream((PipedInputStream) rawInput);
final PipedInputStream rawServerInput = new PipedInputStream();
rawOutput = new PipedOutputStream(rawServerInput);
new Thread() {
public void run() {
try {
TestServerProt.startSession(rawServerInput, rawServerOutput);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}.start();
} else {
InetAddress ip = InetAddress.getByName("127.0.0.1");
int port = 6789;
InetSocketAddress serverAddress = new InetSocketAddress(ip, port);
socket = new Socket();
socket.connect(serverAddress);
rawInput = socket.getInputStream();
rawOutput = socket.getOutputStream();
}
System.out.println("start checkout");
send("CHKT repname", rawInput, rawOutput);
System.out.println(receiveInt(rawInput, rawOutput));
send("RREV", rawInput, rawOutput);
System.out.println(receiveInt(rawInput, rawOutput));
System.out.println("receiving revision");
System.out.println(receiveString(rawInput, rawOutput));
System.out.println("revision received");
System.out.println(receiveInt(rawInput, rawOutput));
System.out.println("receiving files");
send("RFIL", rawInput, rawOutput);
System.out.println(receiveInt(rawInput, rawOutput));
System.out.println("receiving file: ");
System.out.println(receiveString(rawInput, rawOutput));
System.out.println("success!");
if(!MAKE_STUB)
socket.close();
}
}
服务器代码:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
public class TestServerProt {
private static final boolean PING_PONG = false;
public static void startSession(InputStream rawInput, OutputStream rawOutput) throws IOException {
System.out.println("starting session");
System.out.println(receiveString(rawInput, rawOutput));
send(101, rawInput, rawOutput);
System.out.println(receiveString(rawInput, rawOutput));
System.out.println("sending revision");
send(104, rawInput, rawOutput);
send(createRepString(), rawInput, rawOutput);
System.out.println("sending files");
send(101, rawInput, rawOutput);
System.out.println("sending files");
System.out.println(receiveString(rawInput, rawOutput));
send(103, rawInput, rawOutput);
send("content file 1", rawInput, rawOutput);
System.out.println("success!");
//send(rCode);
}
private static void send(String value, InputStream rawInput, OutputStream rawOutput) throws IOException {
PrintWriter output = new PrintWriter(rawOutput);
output.println(value);
output.flush();
if(PING_PONG) {
BufferedReader input = new BufferedReader(new InputStreamReader(rawInput));
if(!input.readLine().equals(value))
System.err.println("Ping pong failed!");
}
}
private static void send(int value, InputStream rawInput, OutputStream rawOutput) throws IOException {
send(String.valueOf(value), rawInput, rawOutput);
}
private static int receiveInt(InputStream rawInput, OutputStream rawOutput) throws NumberFormatException, IOException {
return Integer.parseInt(receiveString(rawInput, rawOutput));
}
private static String receiveString(InputStream rawInput, OutputStream rawOutput) throws IOException {
BufferedReader input = new BufferedReader(new InputStreamReader(rawInput));
String value = input.readLine();
if(PING_PONG) {
PrintWriter output = new PrintWriter(rawOutput);
output.println(value);
output.flush();
}
return value;
}
public static void main(String[] args) throws IOException {
int port = 6789;
InetSocketAddress serverAddress = new InetSocketAddress(port);
ServerSocket serverSocket = new ServerSocket();
serverSocket.bind(serverAddress);
System.out.println("waiting for client");
Socket clientSocket = serverSocket.accept();
System.out.println("client accepted");
startSession(clientSocket.getInputStream(), clientSocket.getOutputStream());
serverSocket.close();
clientSocket.close();
}
private static String createRepString() {
JSONObject json = new JSONObject();
json.put("revision_nr", new Integer(5));
JSONArray jsonArrayContent = new JSONArray();
JSONObject jsonContent = new JSONObject();
jsonContent.put("filename", "f1.txt");
jsonContent.put("revision_nr", 3);
jsonArrayContent.add(jsonContent);
jsonContent.put("filename", "f2.txt");
jsonContent.put("revision_nr", 1);
jsonArrayContent.add(jsonContent);
jsonContent.put("filename", "f3.txt");
jsonContent.put("revision_nr", 5);
jsonArrayContent.add(jsonContent);
json.put("content", jsonArrayContent);
JSONArray jsonArrayStatus = new JSONArray();
JSONObject jsonStatus = new JSONObject();
json.put("status", jsonArrayStatus);
return json.toJSONString();
}
}
最佳答案
在您的情况下,最重要的问题是您每次阅读时都会创建一个新的 BufferedReader
。问题是 BufferedReader 将用可用数据填满它的整个缓冲区——因为它应该这样做。因此它将从底层流读取超出行尾的部分。
解决方案很简单:只创建一次 BufferedReader
,然后传递它,而不是传递 InputStream
。
关于java - 在 Java 输入/输出流上使用 BufferedReader 时 readline() 阻塞,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/23368475/