CON(4) CON(4)
Name
con, tcp, udp - Network connection boxes
Synopsis
/b/con
/b/tcp
/b/udp
Description
Boxes under /b/proto represent network connection end-points
implemented by the proto protocol. Even datagram based ser-
vices are represented by connection end-point boxes. The
prefix /b/con is used to import different network protocols
under the same set of names.
Applications can use make(2) to create new end-points. A
make under /b/tcp creates a TCP end-point; the same happens
under /b/udp for UDP end-points. Applications that do not
care of the particular protocol used are expected to make
new end-points under /b/con. In what follows, all names
refer to boxes under these prefixes.
Plan B connection boxes are intended to be used under a
client-server model. A client is an application that cre-
ates an end-point to send data to a server. A server is an
application that creates an end-point to receive data from a
client. Clients create boxes named machine:port and then
copy data to them. A copy(2) to machine:port sends data to
that port at that machine. The connection is established on
demand (when copying). If it breaks, Plan B tries to recon-
nect on demand. Servers create boxes named local.N:port to
listen at port for new connection requests, and then copy
data from them. There is no connection acceptance/refusal
mechanism, the system accepts all requests. To simultane-
ously listen for different requests at port, a server can
create multiple local.N:port boxes (with different values
for N).
On connection-oriented protocols, a local.N box can be used
to send data back to the client by copying data into it.
On protocols supporting broadcast the application can create
boxes named any:port to perform a broadcast targetted to
port.
Since the interface does not provide all the set of opera-
tions available for the protocols implemented, there can be
boxes named raw.N:0 providing raw access to the protocol
stack. When using these boxes the application is responsible
for supplying appropriate headers in addition to user data.
CON(4) CON(4)
Special operations such like accepting/refussing connections
are done by copying fake headers into/out of the end-point.
Announces
/b/tcp as /con.
Source
/src/b/*/conbox.c
Bugs
There is no raw box implemented, since no application
requires it yet.
Automatic reconnection should raise an error after N
unsucessful attempts.