HS Sockets C Source Library Features

• TCP and UDP sessions
• Supports multiple sessions operating concurrently
• Supports multiple client and multiple server sessions concurrently
• Asynchronous non-blocking operation
• Source code for Windows, Windows Mobile and Linux OS
• Optional support for secure sockets using OpenSSL
• Hostname to IP address resolution
• Retrieve local connection info: hostname, IP address, local port
• Configurable socket read buffer size
• Flow control: enable / disable reading from a socket
• IP address 32 bit to string and vice versa conversion

How It Works
After the user application initializes HS Sockets library with HsSockInit it can now establish TCP client or server sessions or UDP sessions. When acting as a TCP client, the application calls the HsSockTcpConnect supplying the event callback function. HsSockTcpConnect returns immediately. The application then processes HS Sockets event notifications within the event callback function. Once the TCP connection is accepted by the server, the HS_SOCK_EV_CONNECTED is received and the application can send and receive data. When acting as a TCP server, the application calls the  HsSockTcpListen supplying the event callback function. Again, HsSockTcpListen returns immediately. New incoming TCP connections are indicated via the event callback. When acting as a UDP peer, the application calls HsSockUdpOpen supplying the event callback function. To send data the application simply calls HsSockTcpSend or HsSockUdpSendto. The received data is passed up to the application via the event callback. Internally, HsSock uses non-blocking sockets and two threads, one for listening sessions (server sessions) and one for active socket sessions (either connecting or connected).

API Summary

• HsSockInit
• HsSockCleanUp
• HsSockUdpOpen
• HsSockTcpConnect
• HsSockTcpListen
• HsSockTcpSend
• HsSockUdpSendto
• HsSockClose
• HsSockSetReadSize
• HsSockSetReadEnabled
• HsSockTcpSwitchToSecureMode
• HsSockTcpCheckSecureHandshakeDone
• HsSockTcpCheckPeerCertSimple
• HsSockInetNtoa
• HsSockInetAddr
• HsSockGetDomain
• HsSockGetHostIpByName
• HsSockGetLocalAddress

Secure Sockets Implementation Details
Support for SSL / TLS is implemented in HsSock library using OpenSSL toolkit. HsSock library has a compile option to incude SSL support or not. If SSL support is compiled in, HsSock library interfaces to the OpenSSL API in order to manage SSL connections, secure negotiation and data encryption and decryption. SSL support is optional and it is possible to use HS Sockets 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.