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NAME
SYNOPSIS
const BIO_METHOD *
long
char *
BIO *
long
long
long
long
long
DESCRIPTION
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(3) but not BIO_gets(3). If the close flag is set on an accept BIO, then any active connection on that chain is shut down and the socket closed when the BIO is freed. Calling BIO_reset(3) on an accept BIO will close any active connection and reset the BIO into a state where it awaits another incoming connection. BIO_get_fd(3) and BIO_set_fd(3) can be called to retrieve or set the accept socket. See BIO_s_fd(3).
NOTESWhen an accept BIO is at the end of a chain, it will await an incoming connection before processing I/O calls. When an accept BIO is not at the end of a chain, it passes I/O calls to the next BIO in the chain. When a connection is established, a new socket BIO is created for the connection and appended to the chain. That is the chain is now accept->socket. This effectively means that attempting I/O on an initial accept socket will await an incoming connection then perform I/O on it. If any additional BIOs have been set
using
If a server wishes to process multiple connections (as is normally the case), then the accept BIO must be made available for further incoming connections. This can be done by waiting for a connection and then calling: connection =
BIO_pop(accept); After this call, connection will contain a BIO for the recently established connection and accept will now be a single BIO again which can be used to await further incoming connections. If no further connections will be accepted, the accept can be freed using BIO_free(3). If only a single connection will be processed, it is possible to perform I/O using the accept BIO itself. This is often undesirable however because the accept BIO will still accept additional incoming connections. This can be resolved by using BIO_pop(3) (see above) and freeing up the accept BIO after the initial connection. If the underlying accept socket is
non-blocking and
BIO_ctrl(3) cmd and larg arguments correspond to macros as follows:
RETURN VALUESWhen called on an accept BIO object,
BIO_method_type(3)
returns the constant
EXAMPLESThis example accepts two connections on port 4444, sends messages down each and finally closes both down. BIO *abio, *cbio, *cbio2; ERR_load_crypto_strings(); abio = BIO_new_accept("4444"); /* First call to BIO_accept() sets up accept BIO */ if (BIO_do_accept(abio) <= 0) { fprintf(stderr, "Error setting up accept\n"); ERR_print_errors_fp(stderr); exit(0); } /* Wait for incoming connection */ if (BIO_do_accept(abio) <= 0) { fprintf(stderr, "Error accepting connection\n"); ERR_print_errors_fp(stderr); exit(0); } fprintf(stderr, "Connection 1 established\n"); /* Retrieve BIO for connection */ cbio = BIO_pop(abio); BIO_puts(cbio, "Connection 1: Sending out Data on initial connection\n"); fprintf(stderr, "Sent out data on connection 1\n"); /* Wait for another connection */ if (BIO_do_accept(abio) <= 0) { fprintf(stderr, "Error accepting connection\n"); ERR_print_errors_fp(stderr); exit(0); } fprintf(stderr, "Connection 2 established\n"); /* Close accept BIO to refuse further connections */ cbio2 = BIO_pop(abio); BIO_free(abio); BIO_puts(cbio2, "Connection 2: Sending out Data on second\n"); fprintf(stderr, "Sent out data on connection 2\n"); BIO_puts(cbio, "Connection 1: Second connection established\n"); /* Close the two established connections */ BIO_free(cbio); BIO_free(cbio2); SEE ALSOHISTORY
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