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
70 These functions are convenience procedures for creating channels that
71 communicate over TCP sockets. The operations on a channel are
72 described in the manual entry for Tcl_OpenFileChannel.
73
76 Tcl_OpenTcpClient opens a client TCP socket connected to a port on a
77 specific host, and returns a channel that can be used to communicate
78 with the server. The host to connect to can be specified either as a
79 domain name style name (e.g. www.sunlabs.com), or as a string contain‐
80 ing the alphanumeric representation of its four-byte address (e.g.
81 127.0.0.1). Use the string localhost to connect to a TCP socket on the
82 host on which the function is invoked.
83 The myaddr and myport arguments allow a client to specify an address
85 for the local end of the connection. If myaddr is NULL, then an inter‐
86 face is chosen automatically by the operating system. If myport is 0,
87 then a port number is chosen at random by the operating system.
88 If async is zero, the call to Tcl_OpenTcpClient returns only after the
90 client socket has either successfully connected to the server, or the
91 attempted connection has failed. If async is nonzero the socket is
92 connected asynchronously and the returned channel may not yet be con‐
93 nected to the server when the call to Tcl_OpenTcpClient returns. If the
94 channel is in blocking mode and an input or output operation is done on
95 the channel before the connection is completed or fails, that operation
96 will wait until the connection either completes successfully or fails.
97 If the channel is in nonblocking mode, the input or output operation
98 will return immediately and a subsequent call to Tcl_InputBlocked on
99 the channel will return nonzero.
100 The returned channel is opened for reading and writing. If an error
102 occurs in opening the socket, Tcl_OpenTcpClient returns NULL and
103 records a POSIX error code that can be retrieved with Tcl_GetErrno. In
104 addition, if interp is non-NULL, an error message is left in the inter‐
105 preter's result.
106 The newly created channel is not registered in the supplied inter‐
108 preter; to register it, use Tcl_RegisterChannel. If one of the stan‐
109 dard channels, stdin, stdout or stderr was previously closed, the act
110 of creating the new channel also assigns it as a replacement for the
111 standard channel.
112
115 Tcl_MakeTcpClientChannel creates a Tcl_Channel around an existing,
116 platform specific, handle for a client TCP socket.
117 The newly created channel is not registered in the supplied inter‐
119 preter; to register it, use Tcl_RegisterChannel. If one of the stan‐
120 dard channels, stdin, stdout or stderr was previously closed, the act
121 of creating the new channel also assigns it as a replacement for the
122 standard channel.
123
126 Tcl_OpenTcpServer opens a TCP socket on the local host on a specified
127 port and uses the Tcl event mechanism to accept requests from clients
128 to connect to it. The myaddr argument specifies the network interface.
129 If myaddr is NULL the special address INADDR_ANY should be used to
130 allow connections from any network interface. Each time a client con‐
131 nects to this socket, Tcl creates a channel for the new connection and
132 invokes proc with information about the channel. Proc must match the
133 following prototype:
134 typedef void Tcl_TcpAcceptProc(
135 ClientData clientData,
136 Tcl_Channel channel,
137 char *hostName,
138 int port);
139 The clientData argument will be the same as the clientData argument to
141 Tcl_OpenTcpServer, channel will be the handle for the new channel,
142 hostName points to a string containing the name of the client host mak‐
143 ing the connection, and port will contain the client's port number.
144 The new channel is opened for both input and output. If proc raises an
145 error, the connection is closed automatically. Proc has no return
146 value, but if it wishes to reject the connection it can close channel.
147 Tcl_OpenTcpServer normally returns a pointer to a channel representing
149 the server socket. If an error occurs, Tcl_OpenTcpServer returns NULL
150 and records a POSIX error code that can be retrieved with Tcl_GetErrno.
151 In addition, if the interpreter is non-NULL, an error message is left
152 in the interpreter's result.
153 The channel returned by Tcl_OpenTcpServer cannot be used for either
155 input or output. It is simply a handle for the socket used to accept
156 connections. The caller can close the channel to shut down the server
157 and disallow further connections from new clients.
158 TCP server channels operate correctly only in applications that dis‐
160 patch events through Tcl_DoOneEvent or through Tcl commands such as
161 vwait; otherwise Tcl will never notice that a connection request from a
162 remote client is pending.
163 The newly created channel is not registered in the supplied inter‐
165 preter; to register it, use Tcl_RegisterChannel. If one of the stan‐
166 dard channels, stdin, stdout or stderr was previously closed, the act
167 of creating the new channel also assigns it as a replacement for the
168 standard channel.
169
172 On Unix platforms, the socket handle is a Unix file descriptor as
173 returned by the socket system call. On the Windows platform, the
174 socket handle is a SOCKET as defined in the WinSock API.
175
178 Tcl_OpenFileChannel(3), Tcl_RegisterChannel(3), vwait(n)
179
182 client, server, TCP
183Tcl 8.0 Tcl_OpenTcpClient(3)