C++ Boost ASIO: how to read/write with a timeout?


Solution 1

This has been brought up on the asio mailing lists, there's a ticket requesting the feature as well. To summarize, it is suggested to use asynchronous methods if you desire timeouts and cancellability.

If you cannot convert to asynchronous methods, you might try the SO_RCVTIMEO and SO_SNDTIMEO socket options. They can be set with setsockopt, the descriptor can be obtained with the boost::asio::ip::tcp::socket::native method. The man 7 socket man page says

SO_RCVTIMEO and SO_SNDTIMEO Specify the receiving or sending timeouts until reporting an error. The argument is a struct timeval. If an input or output function blocks for this period of time, and data has been sent or received, the return value of that function will be the amount of data transferred; if no data has been transferred and the timeout has been reached then -1 is returned with errno set to EAGAIN or EWOULDBLOCK just as if the socket was specified to be non-blocking. If the timeout is set to zero (the default) then the operation will never timeout. Timeouts only have effect for system calls that perform socket I/O (e.g., read(2), recvmsg(2), send(2), sendmsg(2)); timeouts have no effect for select(2), poll(2), epoll_wait(2), etc.

Solution 2

I used some asio docs to produce this:

class TimeoutAdjust
  TimeoutAdjust(unsigned int dwTimeout) : m_dwTimeout(dwTimeout) {};

  template<class Protocol>
  int level(const Protocol& p) const {return SOL_SOCKET;}

  template<class Protocol>
  int name(const Protocol& p) const {return SO_SNDTIMEO;}

  template<class Protocol>
  const void* data(const Protocol& p) const {return &m_dwTimeout;}

  template<class Protocol>
  size_t size(const Protocol& p) const {return sizeof(m_dwTimeout);}
  unsigned int m_dwTimeout;


TimeoutAdjust adjust(5000);

I debugged it, and it appears to do what it is supposed to.


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Updated on May 14, 2022


  • Stéphane
    Stéphane 15 days

    From reading other Stack Overflow entries and the boost::asio documentation, I've confirmed that there is no synchronous ASIO read/write calls that also provide an easy-to-use timeout as a parameter to the call.

    I'm in the middle of converting an old-school Linux socket application with select(2) calls that employs timeouts, and I need to do more-or-less the same.

    So what is the best way to do this in boost::asio? Looking at the asio documentation, there are many confusing examples of various things to do with timers, but I'm quite confused.

    I'd love to see a simple-to-read example of this: Read from a socket, but wait for a maximum of X seconds after which the function either returns with nothing, or returns with whatever it was able to read from the socket before the timeout expired.

  • Admin
    Admin over 11 years
    Did you read CH's response to the request? ASIO replicates OS functionality in C++, if you requrie some kind of time-out functionality, you're more than welcome to implement it using the bit-n-pieces ASIO provides.
  • updogliu
    updogliu almost 8 years
    What I read here is that SO_SNDTIMEO takes a timeval, rather than an unsigned int. linux.die.net/man/7/socket
  • ArtHare
    ArtHare almost 8 years
    Ah, the MS docs use a DWORD for SO_SNDTIMEO. Looks like timeval is a pair of long ints, so reader beware. MS docs: msdn.microsoft.com/en-ca/library/windows/desktop/…
  • asim
    asim over 7 years
    After using above code i am getting an exception Exception: set_option: Invalid argument.If you have some reference code then please share the same.