cAsyncSocket wraps OS non-blocking sockets that can be used to implement various network components in VB6 -- clients and servers -- and supports both async and blocking network communications.
contrib folder there are helper classes that build-up on
cAsyncSocket base to provide familiar interfaces for completing common tasks.
For instance class
cWinSockRequest exposes same-named methods, properties and events as the OS provided
WinHttpRequest object but can be used to easily access generic TCP/UDP servers instead.
cTlsClient provides streaming support (familiar
Write methods) for accessing both plain-text TCP servers (e.g. http) and SSL/TLS secured ones (e.g. https) using OS provided SSPI/Schannel implementation w/o any additional dependency (e.g. OpenSSL library).
For simple demo TCP/UDP client/server implementation take a look at
test\Chat folder. Same client and server sides are capable of communicating over reliable TCP channels and fast UDP datagrams.
For sample clients to various network services (https, SMTP over SSL, etc.) open sample project in
Start by including
src\cAsyncSocket.cls in your project to have a convenient wrapper to most WinSock API functions.
Optionally you can add
contrib\cTlsClient.cls to your project for SSL/TLS secured channels and/or
contrib\cWinSockRequest.cls for familiar class methods when accessing TCP/UDP network services.
Sample SMTP with STARTTLS
A working sample with error checking omitted for brevity for accessing smtp.gmail.com over port 587.
At first the communication goes over unencrypted plain-text socket, then later its switched to TLS secured one before issuing last
With New cTlsClient .SetTimeouts 0, 5000, 5000, 5000 .Connect "smtp.gmail.com", 587 Debug.Print .ReadText(); .WriteText "HELO 127.0.0.1" & vbCrLf Debug.Print .ReadText(); .WriteText "STARTTLS" & vbCrLf Debug.Print .ReadText(); .StartTls "smtp.gmail.com" Debug.Print "TLS handshake complete: " & .TlsHostAddress .WriteText "QUIT" & vbCrLf Debug.Print .ReadText(); End With
Produces debug output in
Immediate Window similar to this:
220 smtp.gmail.com ESMTP l8sm10315047wmf.39 - gsmtp 250 smtp.gmail.com at your service 220 2.0.0 Ready to start TLS TLS handshake complete: smtp.gmail.com 221 2.0.0 closing connection l8sm10315047wmf.39 - gsmtp
- Allow client to perform TLS server certificate check
- Allow client to assign client certificate for connection
- Provide UI for end-user to choose suitable certificates from Personal certificate store
- Add wrappers for http and ftp protocols
- Add WinSock control replacement
- Add more samples (incl.
- Refactor subclassing thunk to use msg queue not to re-enter IDE in debug mode