HS POP3 C Source Library

Overview

HS POP3 is a software library written in C (supplied with full source code) which implements the client side of Post Office Protocol Version 3 (POP3) over TCP socket layer according to RFC 1939. Among other features, the library supports user authentication, reception of internet headers and text, message deletion and statistics.

HS POP3 supports secure POP3 over TLS / SSL using two methods: POP3S (used by Gmail) and RFC 2595.

HS POP3 supports extracting binary file attachments in MIME v1.0 base64 format..

The use of HS POP3 C Source Library is Royalty Free.

Features

• POP3 Client Operation
• Server name resolution
• Header Reception & Parsing
• Message Text Reception
• Asynchonous non-blocking Operation
• MIME v1.0 base64 binary file attachments
• Secure POP3 over SSL / TLS using POP3S or RFC 2595
• POP3 COMMANDS: USER, PASS, STAT, LIST, UIDL, RETR, DELE, QUIT, TLS

How It Works

First user application calls HS POP3 initialisation function supplying pointers to callback functions in user code for memory and timer management and for reporting POP3 events to user.

To receive email messages from any POP3 RFC1939 compliant server, the user application calls HsPop3GetMail function, specifying mail server name or IP address, login user name and password.

HS POP3 library then resolves the server name, connects to it and receives message scan list according to RFC1939 standard. Once HS POP3 has a unique message ID from the server, it reports this message ID to user application via callback function. The user application returns a specific value if it wants to receive this message.

At this point HS POP3 will request necessary amount of memory for the message and will receive the complete message into the buffer. Once the message is received, the user code is notified with a callback passing a message structure, containing full message pointer, message length, start of text pointer, length of headers and separate parsed out header information: from field, date field, message id field and subject field.

This process is repeated until all messages are received. HS POP3 library can also delete messages from server if this option is specified.

HS POP3 Library incorporates the necessary state machine, transparency procedures, and server response processing required to comply to a simple and robust POP3 client implementation.

Modular design makes it easy to port HS POP3 protocol module to any environment. HS POP3 internally at a lower layer interfaces to HS Sock library which provides TCP transport services. User application need not worry about Winsock - HS POP3 does all transmission, reception and event handling over socket layer.

API Summary

• HsPop3Init
• HsPop3Destroy
• HsPop3Tick
• HsPop3GetMail
• HsPop3Abort
• HsPop3Continue
• HsPop3GetErrStr
• HsPop3MimeMsgHasAttachments
• HsPop3MimeGetMultiPartInfo
• HsPop3MimeGetTextPart
• HsPop3MimeGetBase64File

Secure POP3 Implementation Details

Secure POP3 over TLS / SSL is implemented using 2 methods:

• Legacy POP3S method (used by Gmail)
• RFC 2595 using TLS command

Support for SSL / TLS is implemented in HsSock library (which is included with HsPop3).

HsSock library has a compile option to incude SSL support or not. Is SSL support is compiled in, HsSock library interfaces to OpenSSL API in order to manage SSL connections, secure negotiation and data encryption and decryption.

OpenSSL binaries are supplied with HSPOP3 Demo application.

In order to compile HS POP3 library with SSL support user must have installed OpenSSL. The HS POP3 project file must be adjusted to point it to the OpenSSL header files from correct directory.

SSL support is optional and it is possible to use HS POP3 without OpenSSL. To do that HsSock compile option must be changed not to include SSL support.

* This product includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit

Customization

Hillstone Software provides additional services for customization, porting and integration of the library code to better suit the needs of your products