t_connect - establish a connection with another transport user
int t_connect(fd, sndcall, rcvcall)
struct t_call *sndcall;
struct t_call *rcvcall;
This function enables a transport user to request a connection to the
specified destination transport user. fd identifies the local transport
endpoint where communication will be established, while sndcall and
rcvcall point to a t_call structure that contains the following members:
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
associated with the newly established connection.
netbuf is described in intro(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 function.
The opt argument 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 zero.
In this case, the provider may use default options.
The udata argument 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 in the connect field of the info argument of t_open or
t_getinfo. If the len [see netbuf in intro(3N)] field of udata is zero
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 [see
netbuf in intro(3N)] 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 from t_connect.
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 (that is, return value of zero) indicates that the
requested connection has been established. However, if O_NDELAY or
O_NONBLOCK is set (via 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 connection establishment procedure by sending a connect request to
the destination transport user.
This function resides within both the X/Open compliant libxnet and the
SVR4 compliant libnsl Network Services libraries. Network Services
applications which require X/Open compliance must link-load with -lxnet.
Network Services applications which require SVR4 compliance must linkload
On failure, t_errno may be set to one of the following:
TBADF The specified file descriptor does not refer to a
TOUTSTATE The function was issued in the wrong sequence.
TNODATA O_NDELAY or O_NONBLOCK was set, so the function
successfully initiated the connection establishment
procedure, but did not wait for a response from the
TBADADDR The specified protocol address was in an incorrect
format or contained invalid information.
TBADOPT The specified protocol options were in an incorrect
format or contained invalid information.
TBADDATA The amount of user data specified was not within the
bounds supported by the transport provider as returned
in the connect field of the info argument of t_open or
TACCES The user does not have permission to use the specified
address or options.
TBUFOVFLW The number of bytes allocated for an incoming argument
is not sufficient to store the value of that argument.
If executed in synchronous mode, the 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 transport
endpoint and requires immediate attention.
TNOTSUPPORT This function is not supported by the underlying
TSYSERR A system error has occurred during execution of this
intro(3N), t_accept(3N), t_alloc(3N), t_getinfo(3N), t_listen(3N),
t_open(3N), t_optmgmt(3N), t_rcvconnect(3N)
t_connect returns 0 on success and -1 on failure and t_errno is set to
indicate the error.
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