CHARS=$(python -c 'print (u"\u0621\u0622\u0623\u0624\u0625\u0626\u0627\u0628\u0629\u062A\u062B\u062C\u062D\u062E\u062F\u0630\u0631\u0632\u0633\u0634\u0635\u0636\u0637\u0638\u0639\u063A\u063B\u063C\u063D\u063E\u063F\u0640\u0641\u0642\u0643\u0644\u0645\u0646\u0647\u0648\u0649\u064A".encode("utf8"))')
A very common error when launching a program that listens on some port is getting “Failed to listen on port X” or “Port X is already in use”.
A very common task while troublshooting software servers installed on Linux, is to check if they are receiving traffic at all! Many times the problem is the firewall is just blocking the incoming traffic. Not finding this quickly and lead to hours fiddling with configuration files and all sorts of complex things.