fail to connect using BSD socket api on IPV6 only network in iOS, if does not bind specific ineterface local address.

Question

HYUN SEOK HWANG OP

Created Aug ’21

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my client application always fail to connect using BSD socket api on ipv6-only network in iOS.

bsd socket api connect fuction always return failure with 65(no route to host)

but if bind socket using specific interface address(en0/ipv6), always succeed to connect.

fail case :

try to connect without binding.
try to connect after binding using "::" , "0:0:0:0:0:0:0":

success case:

try to connect after biding using (en0/ipv6) local address (ex 2404:xxxx:fce:4551:xxxx:79c7:xxxx:xxxx)

Does anyone know fail to connect on ipv6 only in iOS if does not bind specific interface local address.

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Answer 1

Systems Engineer OP

Apple

Aug ’21

Does anyone know fail to connect on ipv6 only in iOS if does not bind specific interface local address.

If you are using a local address then you will need to scope the address to an interface with something like ff02::1%en0.

Having said that, instead of using BSD sockets why not try using nw_connection_t or NWConnection as this API attempts to resolve these specific types of issues that you are dealing with.

Matt Eaton
DTS Engineering, CoreOS
meaton3@apple.com

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