1Tcl_OpenTcpClient(3) Tcl Library Procedures Tcl_OpenTcpClient(3)
2______________________________________________________________________________
6
8 Tcl_OpenTcpClient, Tcl_MakeTcpClientChannel, Tcl_OpenTcpServer - proce‐
9 dures to open channels using TCP sockets
10
12 #include <tcl.h>
13 Tcl_Channel
15 Tcl_OpenTcpClient(interp, port, host, myaddr, myport, async)
16 Tcl_Channel
18 Tcl_MakeTcpClientChannel(sock)
19 Tcl_Channel
21 Tcl_OpenTcpServer(interp, port, myaddr, proc, clientData)
22
25 Tcl_Interp *interp (in) Tcl interpreter to use for
26 error reporting. If non-
27 NULL and an error occurs, an
28 error message is left in the
29 interpreter's result.
30 int port (in) A port number to connect to
32 as a client or to listen on
33 as a server.
34 const char *host (in) A string specifying a host
36 name or address for the
37 remote end of the connec‐
38 tion.
39 int myport (in) A port number for the
41 client's end of the socket.
42 If 0, a port number is allo‐
43 cated at random.
44 const char *myaddr (in) A string specifying the host
46 name or address for network
47 interface to use for the
48 local end of the connection.
49 If NULL, a default interface
50 is chosen.
51 int async (in) If nonzero, the client
53 socket is connected asyn‐
54 chronously to the server.
55 ClientData sock (in) Platform-specific handle for
57 client TCP socket.
58 Tcl_TcpAcceptProc *proc (in) Pointer to a procedure to
60 invoke each time a new con‐
61 nection is accepted via the
62 socket.
63 ClientData clientData (in) Arbitrary one-word value to
65 pass to proc.
66______________________________________________________________________________
67
69 These functions are convenience procedures for creating channels that
70 communicate over TCP sockets. The operations on a channel are
71 described in the manual entry for Tcl_OpenFileChannel.
72 TCL_OPENTCPCLIENT
74 Tcl_OpenTcpClient opens a client TCP socket connected to a port on a
75 specific host, and returns a channel that can be used to communicate
76 with the server. The host to connect to can be specified either as a
77 domain name style name (e.g. www.sunlabs.com), or as a string contain‐
78 ing the alphanumeric representation of its four-byte address (e.g.
79 127.0.0.1). Use the string localhost to connect to a TCP socket on the
80 host on which the function is invoked.
81 The myaddr and myport arguments allow a client to specify an address
83 for the local end of the connection. If myaddr is NULL, then an inter‐
84 face is chosen automatically by the operating system. If myport is 0,
85 then a port number is chosen at random by the operating system.
86 If async is zero, the call to Tcl_OpenTcpClient returns only after the
88 client socket has either successfully connected to the server, or the
89 attempted connection has failed. If async is nonzero the socket is
90 connected asynchronously and the returned channel may not yet be con‐
91 nected to the server when the call to Tcl_OpenTcpClient returns. If the
92 channel is in blocking mode and an input or output operation is done on
93 the channel before the connection is completed or fails, that operation
94 will wait until the connection either completes successfully or fails.
95 If the channel is in nonblocking mode, the input or output operation
96 will return immediately and a subsequent call to Tcl_InputBlocked on
97 the channel will return nonzero.
98 The returned channel is opened for reading and writing. If an error
100 occurs in opening the socket, Tcl_OpenTcpClient returns NULL and
101 records a POSIX error code that can be retrieved with Tcl_GetErrno. In
102 addition, if interp is non-NULL, an error message is left in the inter‐
103 preter's result.
104 The newly created channel is not registered in the supplied inter‐
106 preter; to register it, use Tcl_RegisterChannel. If one of the stan‐
107 dard channels, stdin, stdout or stderr was previously closed, the act
108 of creating the new channel also assigns it as a replacement for the
109 standard channel.
110 TCL_MAKETCPCLIENTCHANNEL
112 Tcl_MakeTcpClientChannel creates a Tcl_Channel around an existing,
113 platform specific, handle for a client TCP socket.
114 The newly created channel is not registered in the supplied inter‐
116 preter; to register it, use Tcl_RegisterChannel. If one of the stan‐
117 dard channels, stdin, stdout or stderr was previously closed, the act
118 of creating the new channel also assigns it as a replacement for the
119 standard channel.
120 TCL_OPENTCPSERVER
122 Tcl_OpenTcpServer opens a TCP socket on the local host on a specified
123 port and uses the Tcl event mechanism to accept requests from clients
124 to connect to it. The myaddr argument specifies the network interface.
125 If myaddr is NULL the special address INADDR_ANY should be used to
126 allow connections from any network interface. Each time a client con‐
127 nects to this socket, Tcl creates a channel for the new connection and
128 invokes proc with information about the channel. Proc must match the
129 following prototype:
130 typedef void Tcl_TcpAcceptProc(
132 ClientData clientData,
133 Tcl_Channel channel,
134 char *hostName,
135 int port);
136 The clientData argument will be the same as the clientData argument to
138 Tcl_OpenTcpServer, channel will be the handle for the new channel,
139 hostName points to a string containing the name of the client host mak‐
140 ing the connection, and port will contain the client's port number.
141 The new channel is opened for both input and output. If proc raises an
142 error, the connection is closed automatically. Proc has no return
143 value, but if it wishes to reject the connection it can close channel.
144 Tcl_OpenTcpServer normally returns a pointer to a channel representing
146 the server socket. If an error occurs, Tcl_OpenTcpServer returns NULL
147 and records a POSIX error code that can be retrieved with Tcl_GetErrno.
148 In addition, if the interpreter is non-NULL, an error message is left
149 in the interpreter's result.
150 The channel returned by Tcl_OpenTcpServer cannot be used for either
152 input or output. It is simply a handle for the socket used to accept
153 connections. The caller can close the channel to shut down the server
154 and disallow further connections from new clients.
155 TCP server channels operate correctly only in applications that dis‐
157 patch events through Tcl_DoOneEvent or through Tcl commands such as
158 vwait; otherwise Tcl will never notice that a connection request from a
159 remote client is pending.
160 The newly created channel is not registered in the supplied inter‐
162 preter; to register it, use Tcl_RegisterChannel. If one of the stan‐
163 dard channels, stdin, stdout or stderr was previously closed, the act
164 of creating the new channel also assigns it as a replacement for the
165 standard channel.
166
168 On Unix platforms, the socket handle is a Unix file descriptor as
169 returned by the socket system call. On the Windows platform, the
170 socket handle is a SOCKET as defined in the WinSock API.
171
173 Tcl_OpenFileChannel(3), Tcl_RegisterChannel(3), vwait(n)
174
176 channel, client, server, socket, TCP
177Tcl 8.0 Tcl_OpenTcpClient(3)