Execute a shell command in C but not through web page - c

Question

I have a program in C/java/html 5
The service file of the program runs as root user and it is on an Archlinux distribution.
I want to have the result IP address that SMB will find and show it in an html page i have.
The part of the code i am interested is this:
sds ns_server_list(sds buffer, sds method, int request_id)
{
FILE *fp = popen("/usr/bin/nmblookup -S \'*\' | grep \"<00>\" | awk \'{print $1}\'", "r");
// returns three lines per server found - 1st line ip address 2nd line name 3rd line workgroup
if (fp == NULL)
{
LOG_ERROR("Failed to get server list");
buffer = jsonrpc_respond_message(buffer, method, request_id, "Failed to get server list", true);
}
If i run the program through shell (./test) and after compile, it returns the results in HTML just fine.
If i run it through the web interface of program and through a service file, it returns these SMB errors in journalctl -xe:
WARNING: no network interfaces found
name_query failed to find name *
ERROR Executing syscmd "/usr/bin/nmblookup -S '*'" failed
SMB.conf
[global]
server string = SMB Server
security = user
guest account = root
map to guest = bad user
log level = 0
load printers = No
syslog = 0
directory mask = 0775
create mask = 0775
browseable = yes
#veto files = /._*/.DS_Store/
interfaces = eth0 192.168.2.0/24
Summarized...
If i run the program through service file and without IP address in SMB.conf i have the errors in journalctl. If i put the IP everything is ok but i do not want to work it like this way (dynamic ip and eth0 do not work, same errors).
If i run the program through shell with the executable compiled file (./test) everything play fine without ip address in smb.conf
Why is that?
Thank you.