IRI - API_HOST does not apply to RECEIVER_PORTs?

Question

we assume that the server has the IP addresses "111.111.111.111" and "222.222.222.222" (host ip) and I want to bind IRI to the ip 111.111.111.111

PORT = 14265
UDP_RECEIVER_PORT = 14600
TCP_RECEIVER_PORT = 15600
API_HOST = 111.111.111.111

but netstat -tulpen shows

Proto Recv-Q Send-Q Local Address           Foreign Address         State       User       Inode      PID/Program name
tcp        0      0 0.0.0.0:15600           0.0.0.0:*               LISTEN      1000       20735      662/java
tcp        0      0 111.111.111.111:14265   0.0.0.0:*               LISTEN      1000       20757      662/java
udp        0      0 0.0.0.0:14600           0.0.0.0:*                           1000       20729      662/java

which leads to the problem that my neighbors are trying to communicate with 222.222.222.222 which is the host (not IRI) ip.

 ***** NETWORK ALERT ***** TCP connection reset by neighbor 222.222.222.222, source closed, Connection reset

Answer 1

IRI works in simplex mode, meaning that one TCP connection is used for receiving and another for sending.

Your IRI TCP and UDP receivers are automatically bound to both IP addresses via "catch-all" 0.0.0.0 address. This means that your neighbours can select which IP they prefer (provided that both are open to the public, of course). TCP and UDP receiver addresses therefore have no influence on the IP address that is visible to your peers when they are sending packets to you.

As for your outgoing traffic - IP address which is visible to your neighbours when you are connecting/sending packets to them) - a quick glance at the IRI source code reveals that IRI does not implement socket source address binding before connecting, therefore the source address selection is left to your operating system. This is quite normal.

I assume you're running IRI on Linux;

• If you want to change the default outgoing IP address for all outgoing connections, you can use ip route command (e.g. ip route change default via <default gw> src <your new source addr.>), or
• you can use iptables SNAT target for more specific address selection based on various source/destination address, port, etc. criteria (e.g. iptables -t nat -A POSTROUTING --destination <destionation address> -j SNAT --to-source <your new source address>).