Java DataInputStream 读取不返回

Question

我正在实现一个简单的客户端/服务器读取器，并使用 DataInputStream 将所有内容读取为字节，然后稍后进行解析。

这是我的阅读代码:

String line;
String requestString = "";

//client is a Socket that is initialized elsewhere
DataInputStream inputData = new DataInputStream(client.getInputStream());
byte [] messageByte = new byte[1024];
int counter = 0;
  while(true) {  
    int bytesRead = inputData.read(messageByte, counter, 1024-counter);
    counter = (counter + bytesRead)%1024;
    if(bytesRead == -1) {
      System.out.println("Breaking out of loop");
      break;
    }
    line = new String(messageByte, 0, bytesRead);
    System.out.println( "GOT > " + line );
  }

它能够读取消息，但无法跳出循环，因为最后一次调用 read 没有返回。

Answer 1

套接字将阻塞，直到没有更多输入。 InputStream 只是一个接口(interface)，确切的行为取决于其提供者的实现。在您的套接字上设置超时，以便在一段时间内没有输入时抛出异常。

这里引用自 javadoc on Socket ，请注意，它将从套接字读取的行为描述为阻塞操作，直到达到超时:

public void setSoTimeout(int timeout)
                  throws SocketException

Enable/disable SO_TIMEOUT with the specified timeout, in milliseconds. With this option set to a non-zero timeout, a read() call on the InputStream associated with this Socket will block for only this amount of time. If the timeout expires, a java.net.SocketTimeoutException is raised, though the Socket is still valid. The option must be enabled prior to entering the blocking operation to have effect. The timeout must be > 0. A timeout of zero is interpreted as an infinite timeout.

解决办法:

除了检查 -1 之外，这是可以的。在套接字上设置超时并确保抛出的异常得到正确处理。