Here is a much simpler approach of retrieving the Phone's IP address instead of externally saving it as config file;
FILE* ffile = popen("netstat -rn|awk '$2~/192\\.168\\.43\\.[0-9]{1,3}/ {print $2}'", "r");
pbuffer[0] = 0;
fgets(pbuffer, 100, ffile);
pclose(ffile);
cli_addr.sin_addr.s_addr = inet_addr(pbuffer);