Сохраненная страница Overriding the default Linux kernel 20-second TCP socket connect timeout - sekuda.com (8 Kb)

Whatever language or client library you're using, you should be able to set the timeout on network socket operations, typically split into a connect timeout, read timeout, and write timeout. However, although you should be able to make these timeouts as small as you want, the connect timeout in particular has an effective maximum value for any given kernel. Beyond this point, higher timeout values you might request will have no effect - connecting will still time out after a shorter time. The reason TCP connects are special is that the establishment of a TCP connection has a special sequence of packets starting with a SYN packet. If no response is received to this initial SYN packet, the kernel needs to retry, which it may have to do a couple of times. All kernels I know of wait an increasing amount of time between sending SYN retries, to avoid flooding slow hosts.