Sockets implementations not always perfect and some of them may be broken in various ways. This test suite check ability to correctly retrieve last received data from system after remote side closed TCP connection.

Consider following scenario: TCP connection is established between Host A and Host B. Application on Host A sends some data to Host B and closed connection from side of Host A. On Host B application send some data to Host A and use recv() only after sending. With correct socket implementation, last data, received from Host A, must be returned with this call of recv(). With incorrect socket implementation, Host B detects closure of connection by remote side when sending data and starts return error on any socket operation, including recv(), while received data is present in system socket buffers.

A real world example: HTTP client sending a POST request (request header + request body) to HTTP server. HTTP server detects incorrect header (or unsupported options) after HTTP header is received (request body is still transmitting). HTTP server send 400/406 or 501 error response to client and closed connection. HTTP client in the same time continue to sending request body and starts reading from system received data only after sending full request. If sockets are implemented incorrectly, server response is received by client's system but never returned to client application after system detects remote closure of connection. So application (HTTP client) got only system error "socket was closed by remote side" instead of properly received server response. Correct sockets implementation returns received data even after detection of TCP connection closure by remote side.

Build server_part and clint_part by Visual Studio 2015 or later or by system make (compiler and linker must be installed). Nmake is not supported - use check_system_socket_recv_last.sln solution or MinGW/Cygwin make.

Several combinations of OSes were tested. Current test results:

• FAILED - client_part running on Windows; server_part running on any of: Windows, Linux, FreeBSD, Darwin
• SUCCEED - client_part running on any of: Linux, FreeBSD, Darwin; server_part running on any of: Windows, Linux, FreeBSD, Darwin