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设置连接超时

public void setConnectTimeout (int timeout)

设置打开指向此urlconnection引用的资源的通信链接时要使用的指定超时值（以毫秒为单位）。如果超时在建立连接之前过期，则会引发java.net.sockettimeoutexception。超时为零被解释为无限超时。
解决方案
当客户端无法在超时时间内连接到服务器时，应用程序将抛出 SocketTimeoutException ，因此我们可以使用此行为切换到备份服务器。

String mainUrl = "http://" + IPADDR + "/" + NMSERVER + "/loginNIKUUID.inc.php";
String backupUrl = "http://" + IPADDR2 + "/" + NMSERVER2 + "/loginNIKUUID.inc.php";

@Override
protected String doInBackground(String... params) {
    return connect(mainUrl, params);
}

private String connect(String hostUrl, String...params) {
    try {
        // Enter URL address where your php file resides
        url = new URL(hostUrl);
    } catch (MalformedURLException e) {
        e.printStackTrace();
        return "exception";
    }

    try {
        // Setup HttpURLConnection class to send and receive data from php and mysql
        conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(READ_TIMEOUT);
        conn.setConnectTimeout(CONNECTION_TIMEOUT);
        conn.setRequestMethod("POST");

        // setDoInput and setDoOutput method depict handling of both send and receive
        conn.setDoInput(true);
        conn.setDoOutput(true);

        // Append parameters to URL
        Uri.Builder builder;
        builder = new Uri.Builder();
        //builder.appendQueryParameter("imei", params[0]);
        builder.appendQueryParameter("nik", params[0]);
        builder.appendQueryParameter("uuid", params[1]);
        builder.appendQueryParameter("password", params[2]);
        String query = builder.build().getEncodedQuery();

        // Open connection for sending data
        OutputStream os = conn.getOutputStream();
        BufferedWriter writer = new BufferedWriter(
                new OutputStreamWriter(os, StandardCharsets.UTF_8));
        writer.write(query);
        writer.flush();
        writer.close();
        os.close();
        conn.connect();
    } catch (SocketTimeoutException e) {
        e.printStackTrace();

        // There is a problem with the main server, switch to backup server
        if (hostUrl.equals(mainUrl)) {
            return connect(backupUrl, params);
        }

        return "exception";
    } catch (IOException e) {
        e.printStackTrace();
        return "exception";
    }

    return "success";
}