udp-socket-connect 1 user commands nosh udp-socket-connect connect a socket to a UDP server and chain udp-socket-connect --verbose --local-name name --local-address address --local-port port --numeric-host --numeric-service --check-interfaces --no-kill-IP-options host service next-prog udp-socket-connect is a chain-loading utility that opens a UDP socket, connects it to host and service with connect3, and then chain loads to next-prog with the execvp3 function, having set up I/O and environment variables per the UCSPI conventions. next-prog may contain its own command line options, which udp-socket-connect will ignore. If the --numeric-host command line option is used, then no name lookup is done on host and it must be (a human readable form of) an IP address. If the --numeric-service command line option is used, then no name lookup is done on service and it must be a port number. Otherwise, host is looked up using the system name resolution facility and port can be an alphanumeric service name. The --check-interfaces option prevents the use of any IPv4 addresses if there are no IPv4 addresses on any network interface, and the use of any IPv6 addresses if there are no IPv6 addresses. This isn't particularly useful on a dynamically configured system where network interface IP addresses can come and go. If the --verbose option is used, udp-socket-connect logs information about connections made. The --no-kill-IP-options command line option sets options on the connected socket. It permits IP options (which are removed by default) so that clients can set source routes. next-prog is expected to follow the UCSPI conventions: standard input, output, and error are the same as whatever udp-socket-connect inherited; file descriptors 6 and 7 are (respectively) reading from and writing to the connected socket, which it should treat as generic I/O streams and not expect to be a socket; and information about the local and remote ends of the connected socket is in environment variables. Whatever tcp-socket-connect itself inherited as file descriptors 6 and 7 is closed. udp-socket-connect obtains information about the local socket connection using the getpeername2 and getsockname2 library functions, and sets up the UCSPI-UDP conventional environment variables as follows: PROTO This always has the value UDP, indicating the prefix to the names of the remaining environment variables. UDPLOCALIP The local (client) IP address of the connecting socket, in human-readable form. Normally, the operating system assigns this; but an explicit assignment can be requested with the --local-address command-line option, where address is a numeric IP address that is available and matches the protocol of the remote end. UDPLOCALPORT The local (client) port number of the connecting socket. Normally, the operating system assigns this; but an explicit assignment can be requested with the --local-port command-line option, where port is a numeric port number. UDPLOCALHOST The value of name set by the --local-name option; guaranteed unset if that option is not used. UDPREMOTEIP The remote (server) IP address of the connected socket, in human-readable form. UDPREMOTEPORT The remote (server) port number of the connected socket. UDPREMOTEINFO Guaranteed unset. UDPREMOTEHOST Guaranteed unset. In the 21st century Internet, remote user account information and even host name information are attacker-supplied data and must not be expected by a UCSPI-TCP client, let alone relied upon. Even attempting to find out such information can involve contacting potentially malicious servers. udp-socket-connect performs no lookups for such information. Jonathan de Boyne Pollard