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Rpcapd is a daemon (Unix) or service (Win32) that allows the capture and filter part of libpcap to be run on a remote system.
Rpcapd can run in two modes: passive mode (default) and active mode.
In passive mode, the client (e.g., a network sniffer) connects to rpcapd . The client then sends the appropriate commands to rpcapd to start the capture.
In active mode, rpcapd tries to establish a connection toward the client (e.g., a network sniffer). The client then sends the appropriate commands to rpcapd to start the capture.
Active mode is useful in case rpcapd is run behind a firewall and cannot receive connections from the external world. In this case, rpcapd can be configured to establish the connection to a given host, which has to be configured in order to wait for that connection. After establishing the connection, the protocol continues its job in almost the same way in both active and passive mode.
The user can create a configuration file in the same directory as the executable, and put the configuration commands in there. In order for rpcapd to execute the commands, it needs to be restarted on Win32, i.e. the configuration file is parsed only at the beginning. The UNIX version of rpcapd will reread the configuration file upon receiving a HUP signal. In that case, all the existing connections remain in place, while the new connections will be created according to the new parameters.
In case a user does not want to create the configuration file manually, they can launch rpcapd with the desired flags plus "-s filename" . Rpcapd will parse all the parameters and save them into the specified configuration file.
The remote daemon is installed automatically when installing WinPcap. The installation process places the rpcapd executable file into the WinPcap folder. This file can be executed either from the command line, or as a service. For instance, the installation process updates the list of available services list and it creates a new item (Remote Packet Capture Protocol v.0 (experimental)). To avoid security problems, the service is inactive and it has to be started manually (control panel - administrative tools - services - start).
The service has a set of "standard" parameters, i.e. it is launched with the -d flag (in order to make it run as a service) and the "-f rpcapd.ini" flag.
The rpcapd executable can be launched directly, i.e. it can run in the foreground as well (not as a daemon/service). The procedure is quite simple: you have to invoke the executable from the command line with all the requested parameters except for the -d flag. The capture server will start in the foreground.
-b " address" Bind to the IP address specified by address (either numeric or literal). By default, rpcapd binds to all local IPv4 and IPv6 addresses.
-p " port" Bind to the port specified by port . By default, rpcapd binds to port 2002.
-4 Listen only on IPv4 addresses. By default, rpcapd listens on both IPv4 and IPv6 addresses.
-l " host_list" Only allow hosts specified in the host_list argument to connect to this server. host_list is a list of host names or IP addresses, separated by commas. We suggest that you use host names rather than literal IP addresses in order to avoid problems with different address families.
-n Permit NULL authentication (usually used with -l ).
-a " host" , "port" Run in active mode, connecting to host host on port port . In case port is omitted, the default port (2003) is used.
-v Run in active mode only; by default, if -a is specified, rpcapd it accepts passive connections as well.
-d Run in daemon mode (UNIX only) or as a service (Win32 only). Warning (Win32): this flag is specified automatically when the service is started from the control panel.
-i Run in inetd mode (UNIX only).
-D Log debugging messages.
-s " config_file" Save the current configuration to config_file in the format specified by rpcapd-config (@MAN_FILE_FORMATS@).
-f " config_file" Load the current configuration from config_file in the format specified by rpcapd-config (@MAN_FILE_FORMATS@) and ignore all flags specified on the command line.
-h Print this help screen.
If rpcapd was compiled with SSL support, the following options are also available:
-S Require that SSL be used on connections.
-C With SSL enabled, XXX - I'm not sure how *fetching* the list of compression mechanisms does anything to compression.
-S ssl_keyfile With SSL enabled, use ssl_keyfile as the SSL key file.
-X ssl_certfile With SSL enabled, use ssl_certfile as the SSL certificate file.