BIO_s_accept() returns the accept BIO method. This is a wrapper round the platform's TCP/IP socket accept routines.Using accept BIOs, TCP/IP connections can be accepted and data transferred using only BIO routines. In this way any platform specific operations are hidden by the BIO abstraction.
Read and write operations on an accept BIO will perform I/O on the underlying connection. If no connection is established and the port (see below) is set up properly then the BIO waits for an incoming connection.
Accept BIOs support BIO_puts() but not BIO_gets().
If the close flag is set on an accept BIO then any active connection on that chain is shutdown and the socket closed when the BIO is freed.
Calling BIO_reset() on a accept BIO will close any active connection and reset the BIO into a state where it awaits another incoming connection.
BIO_get_fd() and BIO_set_fd() can be called to retrieve or set the accept socket. See BIO_s_fd(3)
BIO_set_accept_port() uses the string name to set the accept port. The port is represented as a string of the form "host:port", where "host" is the interface to use and "port" is the port. Either or both values can be "*" which is interpreted as meaning any interface or port respectively. "port" has the same syntax as the port specified in BIO_set_conn_port() for connect BIOs, that is it can be a numerical port string or a string to lookup using getservbyname() and a string table.
BIO_new_accept() combines BIO_new() and BIO_set_accept_port() into a single call: that is it creates a new accept BIO with port host_port.
BIO_set_nbio_accept() sets the accept socket to blocking mode (the default) if n is 0 or non blocking mode if n is 1.
BIO_set_accept_bios() can be used to set a chain of BIOs which will be duplicated and prepended to the chain when an incoming connection is received. This is useful if, for example, a buffering or SSL BIO is required for each connection. The chain of BIOs must not be freed after this call, they will be automatically freed when the accept BIO is freed.
BIO_set_bind_mode() and BIO_get_bind_mode() set and retrieve the current bind mode. If BIO_BIND_NORMAL (the default) is set then another socket cannot be bound to the same port. If BIO_BIND_REUSEADDR is set then other sockets can bind to the same port. If BIO_BIND_REUSEADDR_IF_UNUSED is set then and attempt is first made to use BIO_BIN_NORMAL, if this fails and the port is not in use then a second attempt is made using BIO_BIND_REUSEADDR.
BIO_do_accept() serves two functions. When it is first called, after the accept BIO has been setup, it will attempt to create the accept socket and bind an address to it. Second and subsequent calls to BIO_do_accept() will await an incoming connection, or request a retry in non blocking mode.