Java 套接字中收到的延迟响应

Question

我需要有关as400和java连接的帮助。

我在套接字超时异常期间收到延迟响应时遇到问题。因此，当我发送第一个请求并且发生响应超时时，在发送第二个请求后，会收到第一个请求的响应，这会产生差异。

有没有办法在超时异常之后，响应不应该缓存或不应该在下次请求时接收？

下面是我连接到as400服务器的代码片段：

public synchronized static byte[] sendRequestAndGetResponse(byte[] requestBytes) {
    try {
        if(checkHostConnection()){
            LOG.debug("Sending request bytes to Host: {}", Hexifier.toHex(requestBytes));
            IOUtils.write(requestBytes, dos);
            long startTime = System.currentTimeMillis();
            LOG.info("Request sent to host.");
            LOG.info("Waiting on host response");
            byte[] responseLengthBuffer = new byte[4];
            IOUtils.readFully(dis, responseLengthBuffer);
            ByteBuffer bb = ByteBuffer.wrap(responseLengthBuffer);
            int msgLength = bb.getInt();
            byte[] responseRemBytes = new byte[msgLength];
            IOUtils.readFully(dis, responseRemBytes);
            long endTime = System.currentTimeMillis();
            byte[] fullResponseBytes = new byte[responseLengthBuffer.length + responseRemBytes.length];
            System.arraycopy(responseLengthBuffer, 0, fullResponseBytes, 0, responseLengthBuffer.length);
            System.arraycopy(responseRemBytes, 0, fullResponseBytes, responseLengthBuffer.length, responseRemBytes.length);
            LOG.debug("Response from server is received. Time elapsed at {} millis.", (endTime - startTime));
            LOG.debug("Bytes received: {}", Hexifier.toHex(fullResponseBytes));
            return fullResponseBytes;
        } else {
            reconnectToHost();
        }
    } catch (SocketTimeoutException  ste){
        LOG.error("Reading response from socket timeout: {}", ste.getClass().getName());
        try {
            LOG.warn("Waiting for Host reply from its socket timeout.");
            socket.shutdownInput();
            socket.shutdownOutput();
            int hostResponsefromTimeout = dis.read();
            if (hostResponsefromTimeout == -1){
                LOG.debug("Host has responded with -1");
            } else {
                LOG.debug("Host responded with: {}", hostResponsefromTimeout);
            }
        } catch (Exception e){
            LOG.error("Error encountered while trying to validate if Host responded with last timeout.");
           LOG.error(e.getMessage(), e);
        }

        reconnectToHost();
    } catch (EOFException eofe) {
        LOG.debug("An error occurred while reading stream from Host socket connection: {}", eofe.getClass().getName());
        LOG.error(eofe.getMessage(), eofe);
        if (eofe.getMessage() != null && eofe.getMessage().contains("actual: 0")){
            LOG.warn("No bytes were found at stream. Host did not respond.");
        }
        reconnectToHost();
    } catch (SocketException e) {
        LOG.error("An error occurred while attempting to connect to Host: {}", e.getClass().getName());
        LOG.error(e.getMessage(), e);
        if (e.getMessage().contains("Broken pipe")){
            LOG.debug("Connection to Host was lost.");
        }
        reconnectToHost();
    } catch (Exception e) {
        LOG.error(e.getMessage(), e);
        LOG.debug("An error occurred while attempting to connect to Host: {}", e.getClass().getName());
        reconnectToHost();
    }
    return null;
}

Answer 1

如果您在套接字上收到SocketTimeoutException，否则您计划重用于另一个请求，请关闭它，不要将其重用于另一个请求。摆脱所有关闭并读取 catch 处理程序中的代码，然后关闭套接字。您不可能在同一套接字上获得后续请求的"错误响应"。

如果超时次数很多，则超时时间太短。通常，它应该是相关请求的预期服务时间的两倍。