12-10-2018
How to block first bash script until second bash script script launches web server/site?
I'm new to utilities like socat and netcat and I'm not clear if they will do what I need.
I have a "compileDeployStartWebServer.sh" script and a "StartBrowser.sh" script that are started by emacs/elisp at the same time in two different processes.
I'm using Cygwin bash on Windows 10.
My compileDeployStartWebServer.sh compiles the java code and starts the web server on port 8080.
Presently, the "StartBrowser.sh" sleeps for 40 seconds and launches a browser like Chrome or Firefox while the "compileDeployStartWebServer.sh" downloads any dependencies using maven or gradle, compiles the code and starts the web server. This takes a while!
So my plan was to enhance the java startup code in the web site to write "starting" to a UDP socket on port 7777. Alternatively, the java startup code could spawn a new child thread to write "starting" to a TCP socket so it the web site startup code won't block on the TCP socket in case I decide to run without the "StartBrowser.sh" script.
So is there a way to enhance the "StartBrowser.sh" to block on the TCP (or UDP) socket instead of sleeping? I could write some more java code, I suppose.
What would you recommend? UDP? TCP? What could I use to block the "StartBrowser.sh" (besides more custom java code) while the other script is busy downloading dependencies, compiling, deploying and starting the web server? flock?, exec? netcat? socat? something else?
Perhaps I should be using mutexes or semaphores instead? I don't think java has good support for these features, however.
Thanks
Siegfried
Last edited by siegfried; 12-10-2018 at 10:25 PM..
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udp(7) Miscellaneous Information Manual udp(7)
NAME
udp - Internet user datagram protocol (UDP)
SYNOPSIS
#include <sys/socket.h> #include <netinet/in.h>
The following is the socket call for AF_INET sockets:
s = socket(AF_INET, SOCK_DGRAM, 0); The following is the socket call for AF_INET6 sockets:
s = socket(AF_INET6, SOCK_DGRAM, 0);
DESCRIPTION
UDP is a simple, unreliable datagram protocol that is used to support the SOCK_DGRAM abstraction for the Internet Protocol family. UDP
sockets are connectionless, and are normally used with the sendto() and recvfrom() functions, though the connect() function may also be
used to fix the destination for future packets, in which case the recv() or read() and send() or write() functions may be used.
UDP address formats are identical to those used by TCP. In particular, UDP provides a port identifier in addition to the normal Internet
address format. Note that the UDP port space is separate from the TCP port space (that is, a UDP port may not be "connected" to a TCP
port). In addition, IPv4 broadcast packets may be sent (assuming the underlying network supports this) by using a reserved "broadcast
address"; this address is network interface dependent. There is no broadcast address in IPv6.
Options at the IP transport level may be used with UDP; see the ip() reference page.
ERRORS
If a socket operation fails, errno may be set to one of the following values: An attempt was made to create a socket with a port that has
already been allocated. An attempt was made to create a socket with a network address for which no network interface exists. The socket
is already connected. This error occurs when trying to establish connection on a socket or when trying to send a datagram with the desti-
nation address specified. The system ran out of memory for an internal data structure. The destination address of a datagram was not
specified, and the socket has not been connected.
RELATED INFORMATION
Functions: getsockopt(2), recv(2), send(2), socket(2)
Files: netintro(7), inet(7), ip(7) delim off
udp(7)