undefined reference error in g++ - c++

Question

i have the following code:
#include "Poco/Net/DatagramSocket.h"
#include "Poco/Net/SocketAddress.h"
#include "Poco/Timestamp.h"
#include "Poco/DateTimeFormatter.h"
int main(int argc, char** argv)
{
Poco::Net::SocketAddress sa("127.0.0.1", 8080);
Poco::Net::DatagramSocket dgs(sa);
std::string syslogMsg;
Poco::Timestamp now;
syslogMsg = Poco::DateTimeFormatter::format(now,
"<14>%w %f %H:%M:%S Hello, world!");
return 0;
}
and after compiling i get the following errors:
/tmp/cc38RdWw.o: In function `main':
pocoSender.cpp:(.text+0x4d): undefined reference to `Poco::Net::SocketAddress::SocketAddress(std::string const&, unsigned short)'
pocoSender.cpp:(.text+0x7d): undefined reference to `Poco::Net::DatagramSocket::DatagramSocket(Poco::Net::SocketAddress const&, bool)'
pocoSender.cpp:(.text+0x93): undefined reference to `Poco::Timestamp::Timestamp()'
pocoSender.cpp:(.text+0x11f): undefined reference to `Poco::Timestamp::~Timestamp()'
pocoSender.cpp:(.text+0x135): undefined reference to `Poco::Net::DatagramSocket::~DatagramSocket()'
pocoSender.cpp:(.text+0x140): undefined reference to `Poco::Net::SocketAddress::~SocketAddress()'
pocoSender.cpp:(.text+0x163): undefined reference to `Poco::Net::SocketAddress::~SocketAddress()'
pocoSender.cpp:(.text+0x1ac): undefined reference to `Poco::Timestamp::~Timestamp()'
pocoSender.cpp:(.text+0x1ca): undefined reference to `Poco::Net::DatagramSocket::~DatagramSocket()'
pocoSender.cpp:(.text+0x1d9): undefined reference to `Poco::Net::SocketAddress::~SocketAddress()'
/tmp/cc38RdWw.o: In function `Poco::DateTimeFormatter::format(Poco::Timestamp const&, std::string const&, int)':
pocoSender.cpp:(.text._ZN4Poco17DateTimeFormatter6formatERKNS_9TimestampERKSsi[_ZN4Poco17DateTimeFormatter6formatERKNS_9TimestampERKSsi]+0x15): undefined reference to `Poco::DateTime::DateTime(Poco::Timestamp const&)'
pocoSender.cpp:(.text._ZN4Poco17DateTimeFormatter6formatERKNS_9TimestampERKSsi[_ZN4Poco17DateTimeFormatter6formatERKNS_9TimestampERKSsi]+0x43): undefined reference to `Poco::DateTime::~DateTime()'
pocoSender.cpp:(.text._ZN4Poco17DateTimeFormatter6formatERKNS_9TimestampERKSsi[_ZN4Poco17DateTimeFormatter6formatERKNS_9TimestampERKSsi]+0x52): undefined reference to `Poco::DateTime::~DateTime()'
/tmp/cc38RdWw.o: In function `Poco::DateTimeFormatter::format(Poco::DateTime const&, std::string const&, int)':
pocoSender.cpp:(.text._ZN4Poco17DateTimeFormatter6formatERKNS_8DateTimeERKSsi[_ZN4Poco17DateTimeFormatter6formatERKNS_8DateTimeERKSsi]+0x41): undefined reference to `Poco::DateTimeFormatter::append(std::string&, Poco::DateTime const&, std::string const&, int)'
collect2: error: ld returned 1 exit status
i use the following commandline to compile:
g++ -L/usr/local/lib -lPocoUtil -lPocoFoundation -lPocoNet pocoSender.cpp -o hello
please do not mark the question as duplicate as i have included the required libraries using g++ flags, but i am still getting these errors.

Answer 1

It means that the compiler or linker did not find implementations of these functions. It seems that the corresponding libraries or object modules were not included in building of the project.