URL이 작동 중일 때 "java.net.ConnectException : Connection timed out"예외가 발생하는 이유는 무엇입니까?

URL이 작동 중일 때 "java.net.ConnectException : Connection timed out"예외가 발생하는 이유는 무엇입니까?

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ConnectException: Connection timed out내 코드에서 약간의 빈도를 얻습니다 . 내가 조회하려는 URL이 올라 왔습니다. 일부 사용자에게는 동일한 코드가 작동하지만 다른 사용자에게는 작동하지 않습니다. 한 사용자가이 예외를 받기 시작하면 계속해서 예외가 발생하는 것 같습니다.

다음은 스택 추적입니다.

java.net.ConnectException: Connection timed out
Caused by: java.net.ConnectException: Connection timed out
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
    at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
    at java.net.Socket.connect(Socket.java:516)
    at java.net.Socket.connect(Socket.java:466)
    at sun.net.NetworkClient.doConnect(NetworkClient.java:157)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:365)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:477)
    at sun.net.www.http.HttpClient.<init>(HttpClient.java:214)
    at sun.net.www.http.HttpClient.New(HttpClient.java:287)
    at sun.net.www.http.HttpClient.New(HttpClient.java:299)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:796)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:748)
    at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:673)
    at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(HttpURLConnection.java:840)

다음은 내 코드의 일부입니다.

URLConnection urlConnection = null;
OutputStream outputStream = null;
OutputStreamWriter outputStreamWriter = null;
InputStream inputStream = null;

try {
    URL url = new URL(urlBase);
    urlConnection = url.openConnection();
    urlConnection.setDoOutput(true);

    outputStream = urlConnection.getOutputStream(); // exception occurs on this line
    outputStreamWriter = new OutputStreamWriter(outputStream);
    outputStreamWriter.write(urlString);
    outputStreamWriter.flush();
    inputStream = urlConnection.getInputStream();
    String response = IOUtils.toString(inputStream);
    return processResponse(urlString, urlBase, response);
} catch (IOException e) {
    throw new Exception("Error querying url: " + urlString, e);
} finally {
    IoUtil.close(inputStream);
    IoUtil.close(outputStreamWriter);
    IoUtil.close(outputStream);
}

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연결 시간 초과 (로컬 네트워크 및 여러 클라이언트 시스템 가정)는 일반적으로

a) 송신자에게 "호스트에 대한 경로 없음"과 같은 것을 알리지 않고 단순히 패킷을 먹는 일종의 방화벽

b) 잘못된 네트워크 구성 또는 회선 과부하로 인한 패킷 손실

c) 서버에 과부하가 걸리는 너무 많은 요청

d) a small number of simultaneously available threads/processes on the server which leads to all of them being taken. This happens especially with requests that take a long time to run and may combine with c).

Hope this helps.

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If the URL works fine in the web browser on the same machine, it might be that the Java code isn't using the HTTP proxy the browser is using for connecting to the URL.

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The error message says it all: your connection timed out. This means your request did not get a response within some (default) timeframe. The reasons that no response was received is likely to be one of:

a) The IP/domain or port is incorrect

b) The IP/domain or port (i.e service) is down

c) The IP/domain is taking longer than your default timeout to respond

d) You have a firewall that is blocking requests or responses on whatever port you are using

e) You have a firewall that is blocking requests to that particular host

f) Your internet access is down

g) Your live-server is down i.e in case of "rest-API call".

Note that firewalls and port or IP blocking may be in place by your ISP

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I'd recommend raising the connection timeout time before getting the output stream, like so:

urlConnection.setConnectTimeout(1000);

Where 1000 is in milliseconds (1000 milliseconds = 1 second).

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• try to do the Telnet to see any firewall issue
• perform tracert/traceroute to find number of hops

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I solved my problem with:

System.setProperty("https.proxyHost", "myProxy");
System.setProperty("https.proxyPort", "80");

or http.proxyHost...

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This can be a IPv6 problem (the host publishes an IPv6 AAAA-Address and the users host thinks it is configured for IPv6 but it is actually not correctly connected). This can also be a network MTU problem, a firewall block, or the target host might publish different IP addresses (randomly or based on originators country) which are not all reachable. Or similliar network problems.

You cant do much besides setting a timeout and adding good error messages (especially printing out the hosts' resolved address). If you want to make it more robust add retry, parallel trying of all addresses and also look into name resolution caching (positive and negative) on the Java platform.

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There is a possibility that your IP/host are blocked by the remote host, especially if it thinks you are hitting it too hard.

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The reason why this happened to me was that a remote server was allowing only certain IP addressed but not its own, and I was trying to render the images from the server's URLs... so everything would simply halt, displaying the timeout error that you had...

Make sure that either the server is allowing its own IP, or that you are rendering things from some remote URL that actually exists.

참고URL : https://stackoverflow.com/questions/86824/why-would-a-java-net-connectexception-connection-timed-out-exception-occur-wh