Re: Socket & PrintWriter issue-- writing a float to a C client
"Jean-Francois Briere" <jfbriere@gmail.com> wrote in message
news:1157702176.527004.33610@e3g2000cwe.googlegroups.com...
Rather do:
// Java:
SocketServer listener;
int portNumber;
Socket mySocket;
DataOutputStream outp;
listener= new ServerSocket(portNumber);
mySocket=listener.accept();
outp = new DataOutputStream(mySocket.getOutputStream());
outp.writeFloat(85.6f);
// C:
char buffer[4];
int num;
float flt;
num = read(sockfd, buffer, 4);
memcpy(&flt, buffer, 4);
printf("You returned %f from the server\n", flt);
I hope that was meant as a joke as it is the *WORST* way to do this. It is
non-portable. You are assuming that Java and C use the same binary
representation for their floating point values, which is a completely
unfounded assumption.
Using text is the most portable to transfer floating point values between
heterogenous environments. You can use the standard print conversion, but
that is actually not the most accurate way. It assumes that the receiving
end uses the same size of float. If I were writing float on the Java side
and double on the C side this would actually be introducing inaccuracy. The
standard conversion on the Java side is not the exact value of the float or
double, but the minimum number of digits that will be converted back to that
value using the same precision.
The most portable way to send the exact value is to do:
system.out.println( new BigDecimal( 85.6f ).toString() );
--
Dale King