Is it possible to connect to a server that does not have the websocket transport?

[MathiasDrapier]

Hello,
I have a Socket.io server that works very well, I can connect with different libraries (python, js etc ...).
But with this library I can't connect. The special thing about my server is that it does not implement the WebSocket transport.

I can connect and exchange messages for about 5 seconds, then I am disconnected.

Here is the error I am getting:

io.socket.engineio.client.EngineIOException: xhr poll error
        at io.socket.engineio.client.Transport.onError(Transport.java:65)
        at io.socket.engineio.client.transports.PollingXHR.access$100(PollingXHR.java:26)
        at io.socket.engineio.client.transports.PollingXHR$6$1.run(PollingXHR.java:129)
        at io.socket.thread.EventThread$2.run(EventThread.java:80)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
        at java.lang.Thread.run(Thread.java:761)
     Caused by: java.net.SocketTimeoutException: timeout
        at okio.Okio$4.newTimeoutException(Okio.java:232)
        at okio.AsyncTimeout.exit(AsyncTimeout.java:285)
        at okio.AsyncTimeout$2.read(AsyncTimeout.java:241)
        at okio.RealBufferedSource.indexOf(RealBufferedSource.java:354)
        at okio.RealBufferedSource.readUtf8LineStrict(RealBufferedSource.java:226)
        at okhttp3.internal.http1.Http1Codec.readHeaderLine(Http1Codec.java:215)
        at okhttp3.internal.http1.Http1Codec.readResponseHeaders(Http1Codec.java:189)
        at okhttp3.internal.http.CallServerInterceptor.intercept(CallServerInterceptor.java:88)
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
        at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:45)
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
        at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93)
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
        at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93)
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
        at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:127)
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
        at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:257)
        at okhttp3.RealCall$AsyncCall.execute(RealCall.java:201)
        at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133) 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607) 
        at java.lang.Thread.run(Thread.java:761) 
     Caused by: java.net.SocketException: Socket operation on non-socket
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(SocketInputStream.java:151)
        at java.net.SocketInputStream.read(SocketInputStream.java:120)
        at okio.Okio$2.read(Okio.java:140)
        at okio.AsyncTimeout$2.read(AsyncTimeout.java:237)
        at okio.RealBufferedSource.indexOf(RealBufferedSource.java:354) 
        at okio.RealBufferedSource.readUtf8LineStrict(RealBufferedSource.java:226) 
        at okhttp3.internal.http1.Http1Codec.readHeaderLine(Http1Codec.java:215) 
        at okhttp3.internal.http1.Http1Codec.readResponseHeaders(Http1Codec.java:189) 
        at okhttp3.internal.http.CallServerInterceptor.intercept(CallServerInterceptor.java:88) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:45) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121) 
        at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121) 
        at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:127) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121) 
        at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:257) 
        at okhttp3.RealCall$AsyncCall.execute(RealCall.java:201) 
        at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32) 
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133) 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607) 
        at java.lang.Thread.run(Thread.java:761) 

The last part of the stack trace is not always the same, sometimes I have:

Caused by: java.net.SocketException: Socket closed
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(SocketInputStream.java:151)
        at java.net.SocketInputStream.read(SocketInputStream.java:120)
        at okio.Okio$2.read(Okio.java:140)
        at okio.AsyncTimeout$2.read(AsyncTimeout.java:237)
        at okio.RealBufferedSource.indexOf(RealBufferedSource.java:354) 
        at okio.RealBufferedSource.readUtf8LineStrict(RealBufferedSource.java:226) 
        at okhttp3.internal.http1.Http1Codec.readHeaderLine(Http1Codec.java:215) 
        at okhttp3.internal.http1.Http1Codec.readResponseHeaders(Http1Codec.java:189) 
        at okhttp3.internal.http.CallServerInterceptor.intercept(CallServerInterceptor.java:88) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:45) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121) 
        at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121) 
        at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:127) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121) 
        at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:257) 
        at okhttp3.RealCall$AsyncCall.execute(RealCall.java:201) 
        at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32) 
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133) 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607) 
        at java.lang.Thread.run(Thread.java:761) 

or

Caused by: java.net.SocketTimeoutException: Software caused connection abort
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(SocketInputStream.java:151)
        at java.net.SocketInputStream.read(SocketInputStream.java:120)
        at okio.Okio$2.read(Okio.java:140)
        at okio.AsyncTimeout$2.read(AsyncTimeout.java:237)
        at okio.RealBufferedSource.indexOf(RealBufferedSource.java:354) 
        at okio.RealBufferedSource.readUtf8LineStrict(RealBufferedSource.java:226) 
        at okhttp3.internal.http1.Http1Codec.readHeaderLine(Http1Codec.java:215) 
        at okhttp3.internal.http1.Http1Codec.readResponseHeaders(Http1Codec.java:189) 
        at okhttp3.internal.http.CallServerInterceptor.intercept(CallServerInterceptor.java:88) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:45) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121) 
        at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121) 
        at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:127) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147) 
        at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121) 
        at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:257) 
        at okhttp3.RealCall$AsyncCall.execute(RealCall.java:201) 
        at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32) 
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133) 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607) 
        at java.lang.Thread.run(Thread.java:761) 

[darrachequesne]

Thanks, I could indeed reproduce the behavior.

I guess this is a bug, because a failure to upgrade to WebSocket should not close the connection.

[darrachequesne]

For future readers:

I think this was due to the default readTimeout value of the OkHttp client (10 seconds). It must be increased:

OkHttpClient okHttpClient = new OkHttpClient.Builder()
        .readTimeout(1, TimeUnit.MINUTES) // important for HTTP long-polling
        .build();

IO.Options options = new IO.Options();
options.callFactory = okHttpClient;
options.webSocketFactory = okHttpClient;

Socket socket = IO.socket(URI.create("https://example.com"), options);

See also: socketio/engine.io-client-java@fb531fa

Please reopen if needed.