组合多个变量以作为udp数据包发送

Question

I need to send a packet of data over a UDP connection in C++. The first message I need to send is built up of two 32 bit integers and a 64 bit integer. What is the best way to combine multiple variable types into one block of data ready for sending over a UDP connection?

Answer 1

It depends on the requirements for your network. Do you care about endianness? If you do, you should use not just any serialisatioin, but a safe one in regards to endianness.

Generally, each class/struct sendable through the network should have special methods or overloaded operators to stream them in and out. Ultimately you'll have to use macros/functions like hton/ntoh for streaming primitive types eg int, int64, float, double etc.

Upd: also if your network endpoint applications run on different platforms/compilers, you may have different sizes of int, long, short etc. So when serialising, you'll have to convert your integers to some predefined types with sizes guaranteed to be the same on all supported platforms.

Answer 2

I wrote a DNS resolver by hand in C, and structs is indeed the way I did it. Use bit fields to specify sizes of each piece. More about bit fields: http://msdn.microsoft.com/en-us/library/ewwyfdbe.aspx

Make sure to use hton/ntoh to take care of byte order. More information here; http://www.beej.us/guide/bgnet/output/html/multipage/htonsman.html

In fact, peruse beej's guide -- mucho useful information there!