manual: Move /var/paraslash instructions to Troubleshooting.

[paraslash.git] / web / manual.m4

diff --git a/web/manual.m4 b/web/manual.m4
index 0a5f580a79d4fbe603aa87c90c959e90b4d089ce..b7e059785b193ccb67a1c47d34a6d60143b23229 100644 (file)
--- a/web/manual.m4
+++ b/web/manual.m4
@@ -374,14 +374,6 @@ Finally, tell para_client to connect to server_host:
 
 *Step 2*: Start para_server
 
-Before starting the server make sure you have write permissions to
-the directory /var/paraslash that has been created during installation:
-
-       sudo chown $LOGNAME /var/paraslash
-
-Alternatively, use the --afs-socket Option to specify a different
-location for the AFS command socket.
-
 For this first try, we'll use the info loglevel to make the output
 of para_server more verbose.
 
@@ -426,19 +418,8 @@ You may print the list of all known audio files with
 
 *Step 4*: Configure para_audiod
 
-para_audiod needs to create a "well-known" socket for the clients to
-connect to. The default path for this socket is
-
-       /var/paraslash/audiod_socket.$HOSTNAME
-
-In order to make this directory writable for para_audiod, execute
-as bar@client_host
-
-       sudo chown $LOGNAME /var/paraslash
-
-
-We will also have to tell para_audiod that it should receive the
-audio stream from server_host via http:
+We will have to tell para_audiod that it should receive the audio
+stream from server_host via http:
 
        para_audiod -l info -r '.:http -i server_host'
 
@@ -455,9 +436,16 @@ streamed in which order.
 
 *Troubleshooting*
 
-It did not work? To find out why, try to receive, decode and play the
-stream manually using para_recv, para_filter and para_write as follows.
+If you receive a socket related error on server or audiod startup,
+make sure you have write permissions to the /var/paraslash directory:
+
+       sudo chown $LOGNAME /var/paraslash
 
+Alternatively, use the --afs-socket (para_server) or --socket
+(para_audiod) option to specify a different socket pathname.
+
+To identify streaming problems try to receive, decode and play the
+stream manually using para_recv, para_filter and para_write as follows.
 For simplicity we assume that you're running Linux/ALSA and that only
 MP3 files have been added to the database.
 
@@ -2145,6 +2133,35 @@ maintain state for each listening receiver, multicast often implies
 connectionless transport, which is the reason that it is currently
 only available via UDP.
 
+Abstract socket namespace
+~~~~~~~~~~~~~~~~~~~~~~~~~
+UNIX domain sockets are a traditional way to communicate between
+processes on the same machine. They are always reliable (see above)
+and don't reorder datagrams. Unlike TCP and UDP, UNIX domain sockets
+support passing open file descriptors or process credentials to
+other processes.
+
+The usual way to set up a UNIX domain socket (as obtained from
+socket(2)) for listening is to first bind the socket to a file system
+pathname and then call listen(2), then accept(2). Such sockets are
+called _pathname sockets_ because bind(2) creates a special socket
+file at the specified path. Pathname sockets allow unrelated processes
+to communicate with the listening process by binding to the same path
+and calling connect(2).
+
+There are two problems with pathname sockets:
+
+       * The listing process must be able to (safely) create the
+       socket special in a directory which is also accessible to
+       the connecting process.
+
+       * After an unclean shutdown of the listening process, a stale
+       socket special may reside on the file system.
+
+The abstract socket namespace is a non-portable Linux feature which
+avoids these problems. Abstract sockets are still bound to a name,
+but the name has no connection with file system pathnames.
+
 License
 ~~~~~~~