t_connect - establish a connection with another transport user
int t_connect(fd, sndcall, rcvcall)
struct t_call *sndcall;
struct t_call *rcvcall;
t_connect() enables a transport user to request a connection to the
specified destination transport user. fd identifies the local trans-
port endpoint where communication will be established, while sndcall
and rcvcall point to a t_call() structure which contains the following
struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
sndcall specifies information needed by the transport provider to
establish a connection and rcvcall specifies information that is asso-
ciated with the newly established connection.
The maxlen, len, and buf members of the netbuf structure are described
in t_accept(3N). In sndcall, addr specifies the protocol address of
the destination transport user, opt presents any protocol-specific
information that might be needed by the transport provider, udata
points to optional user data that may be passed to the destination
transport user during connection establishment, and sequence has no
meaning for this function.
On return in rcvcall, addr returns the protocol address associated with
the responding transport endpoint, opt presents any protocol-specific
information associated with the connection, udata points to optional
user data that may be returned by the destination transport user during
connection establishment, and sequence has no meaning for this func-
opt implies no structure on the options that may be passed to the
transport provider. The transport provider is free to specify the
structure of any options passed to it. These options are specific to
the underlying protocol of the transport provider. The user may choose
not to negotiate protocol options by setting the len field of opt to 0.
In this case, the transport provider may use default options.
udata enables the caller to pass user data to the destination transport
user and receive user data from the destination user during connection
establishment. However, the amount of user data must not exceed the
limits supported by the transport provider as returned by t_open(3N) or
t_getinfo(3N). If the len field of udata is 0 in sndcall, no data will
be sent to the destination transport user.
On return, the addr, opt, and udata fields of rcvcall will be updated
to reflect values associated with the connection. Thus, the maxlen
field of each argument must be set before issuing this function to
indicate the maximum size of the buffer for each. However, rcvcall may
be NULL in which case no information is given to the user on return
By default, t_connect() executes in synchronous mode, and will wait for
the destination user's response before returning control to the local
user. A successful return (a return value of 0) indicates that the
requested connection has been established. However, if T_NDELAY is set
(using t_open() or fcntl), t_connect() executes in asynchronous mode.
In this case, the call will not wait for the remote user's response,
but will return control immediately to the local user and return -1
with t_errno set to TNODATA to indicate that the connection has not yet
been established. In this way, the function simply initiates the con-
nection establishment procedure by sending a connect request to the
destination transport user.
0 on success.
-1 on failure and sets t_errno to indicate the error.
TACCES The user does not have permission to use the speci-
fied address or options.
TBADADDR The specified protocol address was in an incorrect
format or contained illegal information.
TBADDATA The amount of user data specified was not within
the bounds allowed by the transport provider.
TBADF The specified file descriptor does not refer to a
TBADOPT The specified protocol options were in an incorrect
format or contained illegal information.
TBUFOVFLW The number of bytes allocated for an incoming argu-
ment is not sufficient to store the value of that
argument. If executed in synchronous mode, the
transport provider's state, as seen by the user,
changes to T_DATAXFER and the connect indication
information to be returned in rcvcall is discarded.
TLOOK An asynchronous event has occurred on this trans-
port endpoint and requires immediate attention.
TNODATA T_NDELAY was set, so the function successfully ini-
tiated the connection establishment procedure, but
did not wait for a response from the remote user.
TNOTSUPPORT This function is not supported by the underlying
TOUTSTATE The function was issued in the wrong sequence.
TSYSERR The function failed due to a system error and set
errno to indicate the error.
intro(3), t_accept(3N), t_getinfo(3N), t_listen(3N), t_open(3N), t_opt-
21 January 1990 T_CONNECT(3N)