c++ - Why QTcpSocket received wrong data? -

i'm writing simple network application. client sending server message server printing in qtextedit , responding client . i'm using qtcpserver , qtcpsocket. there problem can't solve. receiving data quint16 + qtime + qstring sending qbytearrey. use quint16 receiving size of data blocks. , reason when client send server

next block size: 16 (quint16 value) block size: 18  

server get:

next block size: 30073  (quint16 value) block size: 18  

as can see, reason server getting qdatastrem wrong variable value , 30073. don't understand why?

void widget::slotsendtoserver() {     logtextedit->append("slotsendtoserver()");     qbytearray arrblock;     qdatastream serversendstream(&arrblock, qiodevice::readwrite);     qstring messagestr = messagelineedit->text();      serversendstream << quint16(0) << qtime::currenttime()                      << messagestr;      serversendstream.device()->seek(0);     serversendstream << (quint16)(arrblock.size() - sizeof(quint16));      qdebug() << "next_block_size:"              <<(quint16)(arrblock.size() - sizeof(quint16))               << endl              << "full size of byte arrey:" << arrblock.size();      tcpsocket->write(arrblock);     messagelineedit->clear(); }    void widget::slotreadclient() {     logtextedit->append("slotreadclient()");     qtcpsocket *tcpsocket = (qtcpsocket*)sender();     qdatastream clientreadstream(tcpsocket);      while(true)     {         if (!next_block_size)         {             if (tcpsocket->bytesavailable() < sizeof(quint16))             {                 break;             }             clientreadstream >> next_block_size;         }          if (tcpsocket->bytesavailable() < next_block_size)         {             break;         }         qtime   time;         qstring messagetextstr;         clientreadstream >> time >> messagetextstr;          qstring messagecompletestr =                 time.tostring() + " " + "client has sent - "                                  + messagetextstr;         logtextedit->append("message received: ");         logtextedit->append(messagecompletestr);          next_block_size = 0;          sendtoclient(tcpsocket,                      "server response: received \""                        + messagetextstr + "\"");     } } 

you should ensure variable next_block_size initialized 0 each time socket connected.

if don't reuse same qtcpsocket object, can done in widget class constructor, or if do, in slot connected signal connected().