I am using SocketPrim to send a udp packet to each of 254 addresses on a network. The message packets have been preconstructed and placed in a list, whose content has already been checked for correctness and appear to meet the specifications in the appropriate RFC. When I go through the list (using mapM_), sending a packet to each address with sendTo, I get a valid return code from sendTo (used trace to check that) for the addresses from 10.129.129.1 through 10.129.129.239. Address 10.129.129.240, however, fails with the messages Fail: invalid argument Action: sendTo Reason: invalid argument The message "invalid argument" does not appear within the source of SocketPrim, but it does appear in several of the binary files in the library. I've begun to dig around in the source code, but I've taken to hoping that someone out there in Haskell land may be able to point me directly to where (and for what) I should be looking to determine just what triggered those messages. Oh, yes, verson info: ghc-5.00.2, linux (debian testing). Thanks in advance for attention. Murray Gross mgross@dorsai.org