Shortening Socket Timeout Using Timeout::Timeout(N) Does Not Seem to Work for Me

C: socket connection timeout

This article might help:

Connect with timeout (or another use for select() )

Looks like you put the socket into non-blocking mode until you've connected, and then put it back into blocking mode once the connection's established.

void connect_w_to(void) { 
  int res; 
  struct sockaddr_in addr; 
  long arg; 
  fd_set myset; 
  struct timeval tv; 
  int valopt; 
  socklen_t lon; 

  // Create socket 
  soc = socket(AF_INET, SOCK_STREAM, 0); 
  if (soc < 0) { 
     fprintf(stderr, "Error creating socket (%d %s)\n", errno, strerror(errno)); 
     exit(0); 
  } 

  addr.sin_family = AF_INET; 
  addr.sin_port = htons(2000); 
  addr.sin_addr.s_addr = inet_addr("192.168.0.1"); 

  // Set non-blocking 
  if( (arg = fcntl(soc, F_GETFL, NULL)) < 0) { 
     fprintf(stderr, "Error fcntl(..., F_GETFL) (%s)\n", strerror(errno)); 
     exit(0); 
  } 
  arg |= O_NONBLOCK; 
  if( fcntl(soc, F_SETFL, arg) < 0) { 
     fprintf(stderr, "Error fcntl(..., F_SETFL) (%s)\n", strerror(errno)); 
     exit(0); 
  } 
  // Trying to connect with timeout 
  res = connect(soc, (struct sockaddr *)&addr, sizeof(addr)); 
  if (res < 0) { 
     if (errno == EINPROGRESS) { 
        fprintf(stderr, "EINPROGRESS in connect() - selecting\n"); 
        do { 
           tv.tv_sec = 15; 
           tv.tv_usec = 0; 
           FD_ZERO(&myset); 
           FD_SET(soc, &myset); 
           res = select(soc+1, NULL, &myset, NULL, &tv); 
           if (res < 0 && errno != EINTR) { 
              fprintf(stderr, "Error connecting %d - %s\n", errno, strerror(errno)); 
              exit(0); 
           } 
           else if (res > 0) { 
              // Socket selected for write 
              lon = sizeof(int); 
              if (getsockopt(soc, SOL_SOCKET, SO_ERROR, (void*)(&valopt), &lon) < 0) { 
                 fprintf(stderr, "Error in getsockopt() %d - %s\n", errno, strerror(errno)); 
                 exit(0); 
              } 
              // Check the value returned... 
              if (valopt) { 
                 fprintf(stderr, "Error in delayed connection() %d - %s\n", valopt, strerror(valopt) 
); 
                 exit(0); 
              } 
              break; 
           } 
           else { 
              fprintf(stderr, "Timeout in select() - Cancelling!\n"); 
              exit(0); 
           } 
        } while (1); 
     } 
     else { 
        fprintf(stderr, "Error connecting %d - %s\n", errno, strerror(errno)); 
        exit(0); 
     } 
  } 
  // Set to blocking mode again... 
  if( (arg = fcntl(soc, F_GETFL, NULL)) < 0) { 
     fprintf(stderr, "Error fcntl(..., F_GETFL) (%s)\n", strerror(errno)); 
     exit(0); 
  } 
  arg &= (~O_NONBLOCK); 
  if( fcntl(soc, F_SETFL, arg) < 0) { 
     fprintf(stderr, "Error fcntl(..., F_SETFL) (%s)\n", strerror(errno)); 
     exit(0); 
  } 
  // I hope that is all 
}

How to set connection timeout with OkHttp

As of OkHttp3 you can do this through the Builder like so

client = new OkHttpClient.Builder()
    .connectTimeout(10, TimeUnit.SECONDS)
    .writeTimeout(10, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .build();

You can also view the recipe here.

For older versions, you simply have to do this

OkHttpClient client = new OkHttpClient();
client.setConnectTimeout(15, TimeUnit.SECONDS); // connect timeout
client.setReadTimeout(15, TimeUnit.SECONDS);    // socket timeout

Request request = new Request.Builder().url(url).build();
Response response = client.newCall(request).execute();

Be aware that value set in setReadTimeout is the one used in setSoTimeout on the Socket internally in the OkHttp Connection class.

Not setting any timeout on the OkHttpClient is the equivalent of setting a value of 0 on setConnectTimeout or setReadTimeout and will result in no timeout at all. Description can be found here.

As mentioned by @marceloquinta in the comments setWriteTimeout can also be set.

As of version 2.5.0 read / write / connect timeout values are set to 10 seconds by default as mentioned by @ChristerNordvik. This can be seen here.

Pip Install Timeout Issue

PIP has a default timeout of 15 sec, reference guide. Pandas is a relatively big file, at 10MB, and it's dependant Numpy, at 20MB could still be needed (if it is not installed already.). In addition, your network connection may be slow. Therefore, set PIP to take longer time by, for example, giving it 1000 sec:

pip --default-timeout=1000 install pandas

as suggested by @Pouya Khalilzad.

Artificially create a connection timeout error

Connect to an existing host but to a port that is blocked by the firewall that simply drops TCP SYN packets. For example, www.google.com:81.

How to set timeout for http.Get() requests in Golang?

Apparently in Go 1.3 http.Client has Timeout field

client := http.Client{
    Timeout: 5 * time.Second,
}
client.Get(url)

That's done the trick for me.

Shorter timeout on connect

Put the socket into non-blocking mode before calling connect(). When it returns with a WSAEWOULDBLOCK error, call select() with whatever timeout interval you want. If select() reports the socket becomes writable, the connection was successful. If select() reports a timeout instead, close the socket.

SmtpClient Timeout doesn't work

Reproducing your test - it works for me

You asked if anyone has encountered the same problem - I just tried your code on Windows 7, VS 2008 with .NET 2.0 - it worked just fine. With the timeout set to 1, as you have it, I get this error almost immediately:

Unhandled Exception: System.Net.Mail.SmtpException: The operation has timed out
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at mailtimeout.Program.Main(String[] args) in c:\test\mailtimeout\Program.cs:line 29

I think the problem may be that you are expecting something different from timeout. Timeout means that the connection was made successfully, but the response did not come back from the server. This means you need to actually have a server listening on port 25 at your destination, but it doesn't respond. For this test, I use Tcl to create a socket on 25 that did nothing:

c:\> tclsh
% socket -server foo 25

When I changed the timout to 15000, I didn't get the timeout error unti l5s later.

Why Smtp.Timeout has no effect if the connection can't be made

If nothing is listening at port 25, or the host is not reachable, the timeout is not going to happen until at least 20s, when the system.net.tcpclient layer times out. This is below the system.net.mail layer. From an excellent article describing the problem and solution:

You will notice that neither of the two classes, System.Net.Sockets.TcpClient nor System.Net.Sockets.Socket has a timeout to connect a socket. I mean a timeout you can set. .NET Sockets do not provide a Connect Timeout when calling the Connect/BeginConnect method while establishing a Synchronous/Asynchronous socket connection. Instead, connect is forced to wait a very long time before an Exception is thrown if the server it tried to connect to is not listening or if there is any network error. The default timeout is 20 - 30 seconds.

There is no ability to change that timeout from mail (which makes sense, mail servers are usually up), and in fact there's no ability to change the connect from system.net.socket, which is really surprising. But you can do an asynchronous connect, and can then tell if your host is up and the port open. From this MSDN thread, and in particular this post, this code works:

Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IAsyncResult result = socket.BeginConnect("192.168.1.180", 25, null, null);
// Two second timeout
bool success = result.AsyncWaitHandle.WaitOne(2000, true);
if (!success) {
    socket.Close();
    throw new ApplicationException("Failed to connect server.");
}

Is there a way to shorten connect_ex()'s timeout?

By setting a timeout on the socket, socket.connect_ex() becomes a non-blocking operation. That is why you are getting EAGAIN and EALREADY errors when calling connect_ex() repeatedly in a loop - EAGAIN on the first call indicates the connection cannot be completed immediately and is in progress in the background, and then EALREADY on subsequent calls indicates that an existing connection is still in progress and has not completed yet.

Your loop simply runs until the connection finally ends with success or failure, no matter how long that takes. The socket timeout you are setting does not play into that logic.

To do what you are asking for, run your own timer in parallel to the connection loop, and then close the socket if the timer elapses before socket.connect_ex() returns its final result.

Alternatively, get rid of the loop altogether.

Call socket.connect_ex() one time, and if it returns EAGAIN then use select.select() to wait for the connection to complete. It has a timeout parameter. A TCP socket will enter a writable state if a pending connection attempt successfully connects to the server. If select() times out, or reports an error, close the socket instead.

Or, try using socket.create_connection(), which also has a timeout parameter.

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