| Previous | Next |
| WSAENAMETOOLONG | WSAEHOSTUNREACH |
WSAEHOSTDOWN
WSAEHOSTDOWN places the failure at the destination host level. It is different from WSAENETUNREACH, where the local stack lacks a route to the network, and from WSAECONNREFUSED, where a reachable target actively rejects a connection.
Why modern traces may show another code
Microsoft notes that host-down conditions are more likely to appear as WSAETIMEDOUT. IP and TCP also treat some ICMP reachability reports as soft errors rather than immediate proof that a host is permanently unavailable. A multihomed destination can have one failed address while another remains usable.
What to correlate
- The destination IP selected after name resolution and whether alternate addresses were attempted.
- Route and neighbor-resolution state on the client.
- ICMP unreachable messages, TCP SYN retries, and the time from connect start to failure.
- Whether failures affect one host, one address family, or an entire remote network.
A server restart can explain a transient outage, but restarting the client is not a meaningful first fix. Preserve the network evidence and compare the failure with WSAEHOSTUNREACH and WSAETIMEDOUT.
Microsoft: Winsock error codes · IETF: Internet host requirements · IETF: TCP reaction to soft errors
Looking for a different code? Search another status or error code.