On 25.06.21 14:46, Eric Robinson wrote: > Olaf and Scott -- > > Thanks to both of you for your comments. I may have asked my question poorly, > since what you both described is the way I understand TCP to work. There is > no correlation between an incoming connection to tomcat and its outgoing > connection to a database backend, nor would I expect there to be. > > Perhaps a simpler way to ask my question is: when a server has multiple IPs, > which one does tomcat use as its source IP when it initiates a three-way > handshake with a remote machine? > > For example, suppose my server has IP addresses 10.0.0.1 and 10.0.0.2, and my > tomcat connector looks like this... > > <Connector > port="8080" > protocol="HTTP/1.1" > address="10.0.0.2" > connectionTimeout="20000" > redirectPort="8443" > /> > > Tomcat is now listening on IP 10.0.0.2. > > But here's the question. If tomcat needs to initiate a TCP session to a > remote machine (acting as a TCP client), will it use 10.0.0.1 or 10.0.0.2 as > the source IP of the outbound connection? I'm assuming it will use the same > IP that the connector is configured to listen on. > Hi Eric,
again: There's no correlation. Your question boils down to a context-free "which source IP does tomcat use for outgoing connections?". In fact, Tomcat doesn't use any. It just asks the runtime environment (ultimately I'd expect the OS) for a connection to a particular destination, then it uses that. How the connection is then established will depend on * available network adapters * best route to the target address * OS or network configuration It will /not/ depend on any of Tomcat's Connector-configurations whatsoever Olaf >> -----Original Message----- >> From: Olaf Kock <tom...@olafkock.de> >> Sent: Friday, June 25, 2021 3:01 AM >> To: users@tomcat.apache.org >> Subject: Re: Re-Use TCP Source Ports if the Socket is Unique? >> >> >> On 25.06.21 05:19, Eric Robinson wrote: >>> Thanks for the feedback, Daniel. >>> >>> I guess the answer depends on whether the socket libraries use the tomcat >> listening port as the source IP. If you have three tomcat instances >> listening on >> three different IPs, each instance should be able to open a client connection >> using the same source port, as long as each tomcat uses its listening IP as >> the >> source IP of the socket. >>> That's the part I'm still not sure about. >> My expectation is that database connections do not have any correlation >> with the listening port: Technically, DB connection pools can be shared >> across >> all contained Hosts and Connectors /within a single tomcat/, and when >> multiple processes are added to the game, it doesn't really change anything. >> >> In fact, it's not uncommon that there's a public facing network adapter, >> where a http-connector listens, but a completely different network adapter >> for any backend communication - e.g. to the database. All that I expect a >> database driver to do is to specify where it wants to connect to, and the OS >> figures out how that connection needs to be routed. >> That's utterly independent of any http connection that comes in to the same >> process. >> >> So: Don't expect any correlation, and you're safe. >> >> (Note: There /may/ be ways to configure a db-driver to specify a source >> address, but I'd expect that rather to add a potential failure rather than >> anything that I'd want to control. If you interpret such a situation >> differently: >> Please elaborate) >> >> Best, >> >> Olaf >> >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org >> For additional commands, e-mail: users-h...@tomcat.apache.org > Disclaimer : This email and any files transmitted with it are confidential > and intended solely for intended recipients. If you are not the named > addressee you should not disseminate, distribute, copy or alter this email. > Any views or opinions presented in this email are solely those of the author > and might not represent those of Physician Select Management. Warning: > Although Physician Select Management has taken reasonable precautions to > ensure no viruses are present in this email, the company cannot accept > responsibility for any loss or damage arising from the use of this email or > attachments. > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org > --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
