This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.
>To: <address@hidden> >From: "Dan Vietor" <address@hidden> >Subject: LDM port 388 >Organization: UCAR/Unidata >Keywords: 200009082028.e88KSNN04012 Hi Dan, You asked: > I've been asked if the LDM uses both TCP and UDP ports 388? I was > assuming it only used TCP ports but I noticed UDP and TCP ports were > reserved in the /etc/services file. As far as I can tell, the only use of UDP port 388 is to provide support for old LDM version 4 protocol. There is still some use of LDM 4 protocols at sites receiving WSI radar data via a satellite feed: the host that redistributes the WSI data to a local server uses LDM 4 protocols. Here's an answer Glenn gave to this some time ago: The ldm version 4 protocol requires UDP for the FEEDME and NOTIFYME. The ldm version 5 protocol currently uses only TCP. BUT, when we drop support for version 4, we are going to try using UDP for transport. We have some experiments and development planned using broadcast and multicast which will depend on udp. (The rational is that we are network limited, rather than CPU limited. TCP puts more load on the network (and the kernel) and less on the user process. By moving the product assembly up into user space, and using smallish (No network reassembly) UDP packets, we may get better performance.) Whether we will use UDP in this way in the future is unclear, since our multicast developments are still on hold. --Russ