Vb.net client - C Server (Sockets)

Asked by: jaxrpc

hi,

I am trying to write an app that communicates with a server that was written in C. Not knowing C at all so i have some problems understanding the messages in c-style struct format that i need to send from the vb.net side.

The C Server accepts a few structs the code below is 1 of them. How do i send the struct in vb.net to the C server via sockets.

thanks

struct {
DWORD messageType;
UINT length;
STRING reserved1;
UINT reserved2;
UINT errorCode;
UINT errorPosition;
} OIP_ResponseProtocolError;
 
 
//For string there is their own struct
struct {
UINT length
CHAR chars[Length];
} STRING;

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Hi jaxrpc,

For sending data to a server, the client program has absolutely no knowledge (or need to know) what language was used to write the server code. Data is data, no matter where it comes from or goes. From your question/sample, the only thing that we can really do with these C structs is to use them as a model for the data buffer.

Unfortunately, we need to know the operating system where these structures are defined. Objects can change sizes between systems. But, if we assume a 32-bit Windows operating system (most likely) we can define a workable buffer.

Check the comments in the code below. They should give you a hint as to what the objects look like.

And note that you might have to pack/unpack a buffer in VB to pass it on the network. That's beyond my ability to help here.

Good Luck,
Kent

struct {
DWORD messageType;
UINT length;
STRING reserved1;
UINT reserved2;
UINT errorCode;
UINT errorPosition;
} OIP_ResponseProtocolError;
 
//  A DWORD is a double word       -- 2 4-bytes words.
//  A UNIT  is a nunsigned integer -- 1 word 
//  A STRING is another structure  -- (see below)
 
//For string there is their own struct
struct {
UINT length
CHAR chars[Length];
} STRING;
 
//  A CHAR is a 1-byte character
//
//  Note that the STRING structure is non-standard and somewhat dangerous.  The value of the
//  length member can be any integer value.  It does not have to match the actual length
//  of the string, the buffer size, or any other value.  The size of the chars member is
//  undefined.  There is no known value for Length, referenced (presumably) as the size of
//  the character array.

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Vb.net client - C Server (Sockets)

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