Fails to bind on specific IPv4 and IPv6

[dzlabing]

Command line:

./nettest -s -L 213.208.152.31:443 -L [2a01:190:15ff:4::beef:31]:443 -k server.key -c server.crt

• Binding on IPv4 works when only the IPv4 is included, as soon as IPv6 is included it fails.
• why does the code even scan interfaces like lo or bond0 when an address is given?
• address already in use is wrong, there is no service on this IP.
• why does it attempt to multicast on other IPs (join multicast group V4 on wanp0 addr 213.208.152.32)?

To me this looks rather broken.

Log:
2026-01-27 18:26:27 [INFO] - Failed to bind TCP V6 listener: Address already in use (os error 98)
2026-01-27 18:26:27 [INFO] - Failed to bind TCP V4 listener: Address already in use (os error 98). On linux it can be because of IPv4-mapped addresses
2026-01-27 18:26:27 [INFO] - TLS Server will listen on V6 [::]:443
2026-01-27 18:26:27 [INFO] - Failed to bind TLS listener: Address already in use (os error 98)
2026-01-27 18:26:27 [INFO] - TLS Server will listen on [2a01:190:15ff:4::beef:31]:443
2026-01-27 18:26:27 [INFO] - MIO TLS Server will listen on [2a01:190:15ff:4::beef:31]:443
2026-01-27 18:26:27 [DEBUG] - Worker 0: starting
2026-01-27 18:26:27 [DEBUG] - Worker 1: starting
2026-01-27 18:26:27 [DEBUG] - Worker 2: starting
2026-01-27 18:26:27 [DEBUG] - Worker 3: starting
2026-01-27 18:26:27 [DEBUG] - Worker 4: starting
2026-01-27 18:26:27 [DEBUG] - Worker 5: starting
2026-01-27 18:26:27 [DEBUG] - Worker 6: starting
2026-01-27 18:26:27 [DEBUG] - Worker 8: starting
2026-01-27 18:26:27 [DEBUG] - Worker 7: starting
2026-01-27 18:26:27 [DEBUG] - Worker 9: starting
2026-01-27 18:26:27 [DEBUG] - Worker 10: starting
2026-01-27 18:26:27 [DEBUG] - Worker 11: starting
2026-01-27 18:26:27 [DEBUG] - Worker 12: starting
2026-01-27 18:26:27 [DEBUG] - Worker 13: starting
2026-01-27 18:26:27 [DEBUG] - Worker 14: starting
2026-01-27 18:26:27 [DEBUG] - Worker 15: starting
2026-01-27 18:26:27 [DEBUG] - Worker 16: starting
2026-01-27 18:26:27 [DEBUG] - Worker 18: starting
2026-01-27 18:26:27 [DEBUG] - Worker 17: starting
2026-01-27 18:26:27 [DEBUG] - Worker 19: starting
2026-01-27 18:26:27 [DEBUG] - Worker 20: starting
2026-01-27 18:26:27 [DEBUG] - Worker 22: starting
2026-01-27 18:26:27 [DEBUG] - Worker 21: starting
2026-01-27 18:26:27 [DEBUG] - Worker 23: starting
2026-01-27 18:26:27 [DEBUG] - Worker 24: starting
2026-01-27 18:26:27 [DEBUG] - Worker 25: starting
2026-01-27 18:26:27 [DEBUG] - Worker 26: starting
2026-01-27 18:26:27 [INFO] - server_config.server_registration: false
2026-01-27 18:26:27 [DEBUG] - Worker 28: starting
2026-01-27 18:26:27 [INFO] - Starting mDNS service for local network discovery...
2026-01-27 18:26:27 [DEBUG] - Worker 27: starting
2026-01-27 18:26:27 [DEBUG] - mDNS service disabled (use -mdns flag to enable)
2026-01-27 18:26:27 [DEBUG] - Worker 29: starting
2026-01-27 18:26:27 [INFO] - Starting mDNS service...
2026-01-27 18:26:27 [INFO] - TLS available on port 443, will be included in mDNS TXT records
2026-01-27 18:26:27 [INFO] - mDNS TXT properties: {"version": "2.0.0", "tls_port": "443", "tcp_port": "443"}
2026-01-27 18:26:27 [INFO] - IP address: 213.208.152.31
2026-01-27 18:26:27 [INFO] - Announcing service: _nettest._tcp.local. on nettest.local.:443 (TCP port in SRV, TLS port in TXT if available)
2026-01-27 18:26:27 [INFO] - mDNS service started successfully. Service will be discoverable in local network.
2026-01-27 18:26:27 [INFO] - Clients can query for '_nettest._tcp' to get server configuration.
2026-01-27 18:26:27 [DEBUG] - join multicast group V4 on lo addr 127.0.0.1
2026-01-27 18:26:27 [DEBUG] - join multicast group V4 on wanp0 addr 213.208.152.31
2026-01-27 18:26:27 [DEBUG] - join multicast group V4 on wanp0 addr 213.208.152.32
2026-01-27 18:26:27 [DEBUG] - failed to join multicast: 213.208.152.32: PKT join multicast group on addr 213.208.152.32: Address already in use (os error 98). Skipped.
2026-01-27 18:26:27 [DEBUG] - join multicast group V4 on wanp0 addr 213.208.152.33
2026-01-27 18:26:27 [DEBUG] - failed to join multicast: 213.208.152.33: PKT join multicast group on addr 213.208.152.33: Address already in use (os error 98). Skipped.
2026-01-27 18:26:27 [DEBUG] - join multicast group V4 on lan addr 172.21.5.4
2026-01-27 18:26:27 [DEBUG] - mDNS service is active and responding to queries
2026-01-27 18:26:27 [DEBUG] - join multicast group V6 on lo addr ::1 with index 1
2026-01-27 18:26:27 [DEBUG] - join multicast group V6 on wanp0 addr 2a01:190:15ff:4::beef:33 with index 8
2026-01-27 18:26:27 [DEBUG] - join multicast group V6 on wanp0 addr 2a01:190:15ff:4::beef:32 with index 8
2026-01-27 18:26:27 [DEBUG] - failed to join multicast: 2a01:190:15ff:4::beef:32: PKT join multicast group on addr 2a01:190:15ff:4::beef:32: Address already in use (os error 98). Skipped.
2026-01-27 18:26:27 [DEBUG] - join multicast group V6 on wanp0 addr 2a01:190:15ff:4::beef:31 with index 8
2026-01-27 18:26:27 [DEBUG] - failed to join multicast: 2a01:190:15ff:4::beef:31: PKT join multicast group on addr 2a01:190:15ff:4::beef:31: Address already in use (os error 98). Skipped.
2026-01-27 18:26:27 [DEBUG] - join multicast group V6 on wanp0 addr fe80::1270:fdff:fedf:a5ae with index 8
2026-01-27 18:26:27 [DEBUG] - failed to join multicast: fe80::1270:fdff:fedf:a5ae: PKT join multicast group on addr fe80::1270:fdff:fedf:a5ae: Address already in use (os error 98). Skipped.
2026-01-27 18:26:27 [DEBUG] - join multicast group V6 on bond0 addr fe80::7415:19ff:fed2:18f1 with index 10
2026-01-27 18:26:27 [DEBUG] - join multicast group V6 on lan addr fda1:d2f4:a4a6:1::4 with index 11
2026-01-27 18:26:27 [DEBUG] - join multicast group V6 on lan addr fe80::7415:19ff:fed2:18f1 with index 11
2026-01-27 18:26:27 [DEBUG] - failed to join multicast: fe80::7415:19ff:fed2:18f1: PKT join multicast group on addr fe80::7415:19ff:fed2:18f1: Address already in use (os error 98). Skipped.
2026-01-27 18:26:27 [DEBUG] - register service ServiceInfo { ty_domain: "_nettest._tcp.local.", sub_domain: None, fullname: "nettest._nettest._tcp.local.", server: "nettest.local.", addresses: {213.208.152.31}, port: 443, host_ttl: 120, other_ttl: 4500, priority: 0, weight: 0, txt_properties: TxtProperties { properties: [TxtProperty {key: "version", val: Some("2.0.0")}, TxtProperty {key: "tls_port", val: Some("443")}, TxtProperty {key: "tcp_port", val: Some("443")}] }, addr_auto: false, status: {}, requires_probe: true, supported_intfs: [All], is_link_local_only: false }
2026-01-27 18:26:27 [DEBUG] - prepare_announce (ipv4: true): no valid addrs on interface lo
2026-01-27 18:26:27 [DEBUG] - prepare_announce (ipv4: false): no valid addrs on interface lo
2026-01-27 18:26:27 [DEBUG] - prepare to announce service nettest._nettest._tcp.local. on [213.208.152.31]
2026-01-27 18:26:27 [DEBUG] - new probe of nettest._nettest._tcp.local.
2026-01-27 18:26:27 [DEBUG] - insert record TYPE_SRV into probe of nettest._nettest._tcp.local.
2026-01-27 18:26:27 [DEBUG] - insert record TYPE_TXT into probe of nettest._nettest._tcp.local.
2026-01-27 18:26:27 [DEBUG] - new probe of nettest.local.
2026-01-27 18:26:27 [DEBUG] - insert record TYPE_A into probe of nettest.local.
2026-01-27 18:26:27 [DEBUG] - prepare_announce (ipv4: false): no valid addrs on interface wanp0
2026-01-27 18:26:27 [DEBUG] - prepare_announce (ipv4: true): no valid addrs on interface bond0
2026-01-27 18:26:27 [DEBUG] - prepare_announce (ipv4: false): no valid addrs on interface bond0
2026-01-27 18:26:27 [DEBUG] - prepare_announce (ipv4: true): no valid addrs on interface lan
2026-01-27 18:26:27 [DEBUG] - prepare_announce (ipv4: false): no valid addrs on interface lan
2026-01-27 18:26:27 [DEBUG] - tiebreaking 'nettest.local.': Equal
2026-01-27 18:26:27 [DEBUG] - tiebreaking 'nettest._nettest._tcp.local.': Equal
2026-01-27 18:26:27 [DEBUG] - tiebreaking 'nettest.local.': Equal
2026-01-27 18:26:27 [DEBUG] - tiebreaking 'nettest._nettest._tcp.local.': Equal
2026-01-27 18:26:27 [DEBUG] - tiebreaking 'nettest.local.': Equal
2026-01-27 18:26:27 [DEBUG] - tiebreaking 'nettest._nettest._tcp.local.': Equal
2026-01-27 18:26:27 [DEBUG] - tiebreaking 'nettest.local.': Equal
2026-01-27 18:26:27 [DEBUG] - tiebreaking 'nettest._nettest._tcp.local.': Equal
2026-01-27 18:26:28 [DEBUG] - tiebreaking 'nettest.local.': Equal
2026-01-27 18:26:28 [DEBUG] - tiebreaking 'nettest._nettest._tcp.local.': Equal
2026-01-27 18:26:28 [DEBUG] - tiebreaking 'nettest.local.': Equal
2026-01-27 18:26:28 [DEBUG] - tiebreaking 'nettest._nettest._tcp.local.': Equal
2026-01-27 18:26:28 [DEBUG] - probe of 'nettest.local.' finished: move 1 records to active. (1 waiting services)
2026-01-27 18:26:28 [DEBUG] - probe of 'nettest._nettest._tcp.local.' finished: move 2 records to active. (1 waiting services)
2026-01-27 18:26:28 [DEBUG] - prepare to announce service nettest._nettest._tcp.local. on [213.208.152.31]
2026-01-27 18:26:28 [DEBUG] - found active record TYPE_SRV nettest._nettest._tcp.local.
2026-01-27 18:26:28 [DEBUG] - found active record TYPE_TXT nettest._nettest._tcp.local.
2026-01-27 18:26:28 [DEBUG] - found active record TYPE_A nettest.local.
2026-01-27 18:26:28 [DEBUG] - prepare_announce (ipv4: false): no valid addrs on interface wanp0
2026-01-27 18:26:28 [DEBUG] - wake up: announce service nettest._nettest._tcp.local. on wanp0
2026-01-27 18:26:29 [DEBUG] - prepare to announce service nettest._nettest._tcp.local. on [213.208.152.31]
2026-01-27 18:26:29 [DEBUG] - found active record TYPE_SRV nettest._nettest._tcp.local.
2026-01-27 18:26:29 [DEBUG] - found active record TYPE_TXT nettest._nettest._tcp.local.
2026-01-27 18:26:29 [DEBUG] - found active record TYPE_A nettest.local.
2026-01-27 18:26:29 [DEBUG] - prepare_announce (ipv4: false): no valid addrs on interface wanp0
2026-01-27 18:26:29 [DEBUG] - resend: announce service nettest._nettest._tcp.local. on wanp0
2026-01-27 18:26:37 [INFO] - TLS connection added to global queue (queue size: 1)
2026-01-27 18:26:37 [INFO] - Worker 10: taking connection from global queue (queue size after: 0)
2026-01-27 18:26:37 [INFO] - Worker 10: processing connection
2026-01-27 18:26:37 [DEBUG] - Loading certificates from server.crt
2026-01-27 18:26:37 [DEBUG] - Successfully parsed 2 certificates
2026-01-27 18:26:37 [DEBUG] - Loading private key from server.key
2026-01-27 18:26:37 [DEBUG] - Successfully loaded private key: Pkcs8(PrivatePkcs8KeyDer("[secret key elided]"))
2026-01-27 18:26:37 [INFO] - RustlsServerStream created
2026-01-27 18:26:37 [INFO] - Worker 10: registering connection
2026-01-27 18:26:37 [INFO] - Worker 10: handle_greeting_receive_connection_type
2026-01-27 18:26:37 [DEBUG] - decided upon suite TLS13_AES_256_GCM_SHA384
2026-01-27 18:26:37 [DEBUG] - Processed new packets 0
2026-01-27 18:26:37 [DEBUG] - Processed new packets 0
2026-01-27 18:26:37 [DEBUG] - WouldBlock 1
2026-01-27 18:26:37 [DEBUG] - mDNS service is active and responding to queries
2026-01-27 18:26:37 [DEBUG] - Processed new packets 95
2026-01-27 18:26:37 [DEBUG] - Worker 10: is_websocket: false
2026-01-27 18:26:37 [DEBUG] - Worker 10: writing upgrade response
2026-01-27 18:26:37 [DEBUG] - Worker 10: wrote 72 bytes HTTP/1.1 101 Switching Protocols
Connection: Upgrade
Upgrade: RMBT

2026-01-27 18:26:37 [DEBUG] - Worker 10: reregistering stream
2026-01-27 18:26:37 [INFO] - Worker 10: handshake done
2026-01-27 18:26:37 [DEBUG] - Worker 10 registered new connection with token Token(1) (total connections: 1)
2026-01-27 18:26:37 [DEBUG] - handle_greeting_send_version for client [2a01:4f9:5a:1258:deef::1]:46204
2026-01-27 18:26:37 [DEBUG] - handle_greeting_send_version version: RMBTv1.5.0

2026-01-27 18:26:37 [DEBUG] - handle_greeting_send_accept_token
2026-01-27 18:26:37 [DEBUG] - Wrote handle_greeting_send_accept_token 18
^C2026-01-27 18:26:39 [INFO] - Ctrl+C received, shutting down server...
2026-01-27 18:26:39 [INFO] - Shutdown signal received, stopping server...
2026-01-27 18:26:39 [INFO] - Server stopping...
2026-01-27 18:26:39 [INFO] - Starting graceful shutdown...
2026-01-27 18:26:39 [INFO] - Server shutdown complete
2026-01-27 18:26:39 [INFO] - Server stopped
2026-01-27 18:26:39 [DEBUG] - MIO TCP Server shutting down

[olsemeno]

Thanks a lot for the bug report! We’ve pushed a new build (2.0.1) with a fix. Could you please check and confirm if it’s all good on your side?