  A scheme for quantum secure direct communication (QSDC) network is proposed
with a sequence of polarized single photons. The single photons are prepared
originally in the same state |0> by the servers on the network, which will
reduce the difficulty for the legitimate users to check eavesdropping largely.
The users code the information on the single photons with two unitary
operations which do not change their measuring bases. Some decoy photons, which
are produced by operating the sample photons with a Hadamard, are used for
preventing a potentially dishonest server from eavesdropping the quantum lines
freely. This scheme is an economical one as it is the easiest way for QSDC
network communication securely.
