Android:HttpURLConnection 不会断开连接

Question

通过在服务器上运行netstat:
直到几天前:我可以看到连接ESTABLISHED只有大约一秒钟，然后它就会从列表中消失
NOW:它保持 ESTABLISHED 大约 10 秒，然后进入 FIN_WAIT1 和 FIN_WAIT2

Android代码一样，服务器还是一样

是否有可能某种 Android 更新可能改变了一些事情？

我真的无法解释。

我报告下面的代码。 urlConnection.disconnect() 被执行，但连接仍然在服务器上建立。

    HttpURLConnection urlConnection = null;
    System.setProperty("http.keepAlive", "false");

    try {
        URL url = new URL(stringUrl);
        urlConnection = (HttpURLConnection) url.openConnection();
        InputStream instream = new BufferedInputStream(urlConnection.getInputStream());
        ...
        instream.close();
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (urlConnection!=null) {
            urlConnection.disconnect();
        }
    }

Answer 1

当输入流上的所有数据都被消耗时，连接会自动释放并添加到连接池中。底层套接字连接没有释放，假设连接将在不久的将来被重用。在 finally block 中调用 disconnect 是一种很好的做法，因为它负责在出现异常 时释放连接。

这里是FixedLengthInputStream的read方法的实现:

@Override public int read(byte[] buffer, int offset, int count) throws IOException {
        Arrays.checkOffsetAndCount(buffer.length, offset, count);
        checkNotClosed();
        if (bytesRemaining == 0) {
            return -1;
        }
        int read = in.read(buffer, offset, Math.min(count, bytesRemaining));
        if (read == -1) {
            unexpectedEndOfInput(); // the server didn't supply the promised content length
            throw new IOException("unexpected end of stream");
        }
        bytesRemaining -= read;
        cacheWrite(buffer, offset, read);
        if (bytesRemaining == 0) {
            endOfInput(true);
        }
        return read;
    }

当bytesRemaining变量变为0时，endOfInput被调用，它将进一步调用带有 true 参数的 release 方法，这将确保连接被合并。

protected final void endOfInput(boolean reuseSocket) throws IOException {
    if (cacheRequest != null) {
            cacheBody.close();
    }
    httpEngine.release(reuseSocket);
}

这是 release方法实现。 最后一个 if 检查确保连接是否需要关闭或添加到连接池以供重用。

public final void release(boolean reusable) {
    // If the response body comes from the cache, close it.
    if (responseBodyIn == cachedResponseBody) {
        IoUtils.closeQuietly(responseBodyIn);
    }
    if (!connectionReleased && connection != null) {
        connectionReleased = true;
        // We cannot reuse sockets that have incomplete output.
        if (requestBodyOut != null && !requestBodyOut.closed) {
            reusable = false;
        }
        // If the headers specify that the connection shouldn't be reused, don't reuse it.
        if (hasConnectionCloseHeader()) {
            reusable = false;
        }
        if (responseBodyIn instanceof UnknownLengthHttpInputStream) {
            reusable = false;
        }
        if (reusable && responseBodyIn != null) {
            // We must discard the response body before the connection can be reused.
            try {
                Streams.skipAll(responseBodyIn);
            } catch (IOException e) {
                reusable = false;
            }
        }
        if (!reusable) {
            connection.closeSocketAndStreams();
            connection = null;
        } else if (automaticallyReleaseConnectionToPool) {
            HttpConnectionPool.INSTANCE.recycle(connection);
            connection = null;
        }
    }
}

注意:我之前已经回答了几个与 HttpURLConnection 相关的 SO 问题，这可以帮助您理解底层实现。以下是链接:Link1和 Link2 .