| ... E sendto(3, 0x80c2e44, 4, 0, AF=2 224.1.0.1:6666, 16): Network is unreachable |
you have a routing problem. The (Linux) IP stack seems to handle multicast -addresses just like unicast addresses when determining their route (interface and gateway).
+addresses just like unicast addresses when determining their route (interface + and gateway), i.e. the routing table needs an entry that somehow matches the + target address.For the same reason, multicast packets will probably leave your host on the -interface with the default route.
+interface with the default route if it is specified.-Set a multicast/broadcast route with the following command:
+Set a multicast/broadcast route with the following command (Linux): route add -net 224.0.0.0/3 gw 192.168.10.2 - +-224.0.0.1 is the all-systems multicast address: all +224.0.0.1 is the all-systems multicast address: all datagram sockets appear to be automatically member of this group on all -interfaces. This membership cannot be dropped on Linux. +interfaces. This membership cannot be dropped on Linux (you need iptables to +filter packets).
@@ -240,11 +243,11 @@ interfaces. This membership cannot be dropped on Linux.When you use the above examples you should understand that all datagram sockets without exception accept all packets that are directly addressed to them; -the multi- and broadcast receiving features are just extensions to the normal +the multi- and broadcast receiving features are just extensions to this functionality. socat currently has no means to handle incoming packets -differently when it is addressed to a unicast, multicast, or broadcast -address. However, for EXEC'd scripts socat can provide this info in environment -variables. +differently whether they are addressed to unicast, multicast, or broadcast +addresses. However, for EXEC'd scripts socat can provide this info in +environment variables.
Authentication or encryption are not available.
@@ -301,7 +304,51 @@ Please note that the new features could not be successfully tested on IPv6; these sections thus apply to IPv4 only. -This document was last modified in April 2009.
++socat version 1.7.0 helps to find more information about incoming packets in +environment variables that can be used in scripts or programs invoked by +socat. The option ip-pktinfo (on non-BSD systems) +or ip-recvdstaddr (on BSD systems) is required to get basic +information about incoming packets. +
+ ++Example: Start a receiver of the following form (tried on Linux): +
+ + +socat -u udp-recvfrom:8888,reuseaddr,ip-add-membership=224.1.0.1:192.168.10.2,ip-pktinfo,fork system:export + + ++Then send a multicast packet from the client: +
+ + +echo |socat -u - udp-datagram:224.1.0.1:8888 + + ++On the server the following text should appear (only interesting lines shown): +
+ ++export SOCAT_IP_DSTADDR="224.1.0.1" +export SOCAT_IP_IF="eth0" +export SOCAT_IP_LOCADDR="192.168.10.2" +export SOCAT_PEERADDR="192.168.10.1" +export SOCAT_PEERPORT="41159" ++ +
+SOCAT_IP_IF shows the interface where the packet entered the server; +SOCAT_IP_LOCADDR shows the IP address of this interface; +SOCAT_IP_DSTADDR shows the target address of the packet; +SOCAT_PEERADDR and SOCAT_PEERPORT are the client socket +values. +
+This document was last modified in May 2009.
Copyright: Gerhard Rieger 2007-2009
License: GNU Free Documentation License (FDL)