使用 Java 请求超时，但在 cURL 和 postman 上工作

Question

I'm setting up google recaptcha on my java application and I'm getting connect timeout:

Caused by: org.apache.http.conn.ConnectTimeoutException: Connect to www.google.com:443 [www.google.com/172.217.168.164] failed: connect timed out
    at org.apache.http.impl.conn.HttpClientConnectionOperator.connect(HttpClientConnectionOperator.java:134)
    at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:319)
    at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:363)
    at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:219)
    at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:195)
    at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:86)
    at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:108)
    at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:184)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:106)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:57)
    at com.mashape.unirest.http.HttpClientHelper.request(HttpClientHelper.java:138)
HttpClientHelper.java:138
    ... 2 more
Caused by: java.net.SocketTimeoutException: connect timed out
    at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at org.apache.http.conn.ssl.SSLConnectionSocketFactory.connectSocket(SSLConnectionSocketFactory.java:244)
    at org.apache.http.impl.conn.HttpClientConnectionOperator.connect(HttpClientConnectionOperator.java:1

To test if there was any problem with the network, I made the same request using Postman and cURL, both returned the expected response. Then I used postman to generate java code, ran it and got the same error.

Notice that in order for the request to work with Postman I had to turn off "Use System Proxy". This lead me to think that maybe java was using system proxy by default and tried to disable it with System.setProperty("java.net.useSystemProxies", "false"); (also tried with true). Still got same error.

Here is a example of the code used:

 HttpResponse<String> response = Unirest.post("https://www.google.com/recaptcha/api/siteverify")
        .header("response", "abc")
        .header("secret", "abc")
        .asString();

Thanks in advance.

Answer 1

Like so often, the reason was dead simple:

The target server only has an IPv4 address. Java for some reason tries to access the target using IPv6 and fails to do so. I assume that this kind of "halts" the ongoing process and this can only be remedied by aborting the hanging thread (what the timeout effectively does)

As soon as I addded -Djava.net.preferIPv4Stack=true to the call of my program, I was able to run it successfully.

source: HttpClient hits timeout but server is available and working flawlessly

maybe?