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 re‐
37 mote end of the connection.
38 int myport (in) A port number for the
40 client's end of the socket.
41 If 0, a port number is allo‐
42 cated at random.
43 const char *myaddr (in) A string specifying the host
45 name or address for network
46 interface to use for the lo‐
47 cal end of the connection.
48 If NULL, a default interface
49 is chosen.
50 int async (in) If nonzero, the client
52 socket is connected asyn‐
53 chronously to the server.
54 ClientData sock (in) Platform-specific handle for
56 client TCP socket.
57 Tcl_TcpAcceptProc *proc (in) Pointer to a procedure to
59 invoke each time a new con‐
60 nection is accepted via the
61 socket.
62 ClientData clientData (in) Arbitrary one-word value to
64 pass to proc.
65______________________________________________________________________________
66
68 These functions are convenience procedures for creating channels that
69 communicate over TCP sockets. The operations on a channel are de‐
70 scribed in the manual entry for Tcl_OpenFileChannel.
71 TCL_OPENTCPCLIENT
73 Tcl_OpenTcpClient opens a client TCP socket connected to a port on a
74 specific host, and returns a channel that can be used to communicate
75 with the server. The host to connect to can be specified either as a
76 domain name style name (e.g. www.sunlabs.com), or as a string contain‐
77 ing the alphanumeric representation of its four-byte address (e.g.
78 127.0.0.1). Use the string localhost to connect to a TCP socket on the
79 host on which the function is invoked.
80 The myaddr and myport arguments allow a client to specify an address
82 for the local end of the connection. If myaddr is NULL, then an inter‐
83 face is chosen automatically by the operating system. If myport is 0,
84 then a port number is chosen at random by the operating system.
85 If async is zero, the call to Tcl_OpenTcpClient returns only after the
87 client socket has either successfully connected to the server, or the
88 attempted connection has failed. If async is nonzero the socket is
89 connected asynchronously and the returned channel may not yet be con‐
90 nected to the server when the call to Tcl_OpenTcpClient returns. If the
91 channel is in blocking mode and an input or output operation is done on
92 the channel before the connection is completed or fails, that operation
93 will wait until the connection either completes successfully or fails.
94 If the channel is in nonblocking mode, the input or output operation
95 will return immediately and a subsequent call to Tcl_InputBlocked on
96 the channel will return nonzero.
97 The returned channel is opened for reading and writing. If an error
99 occurs in opening the socket, Tcl_OpenTcpClient returns NULL and
100 records a POSIX error code that can be retrieved with Tcl_GetErrno. In
101 addition, if interp is non-NULL, an error message is left in the inter‐
102 preter's result.
103 The newly created channel is not registered in the supplied inter‐
105 preter; to register it, use Tcl_RegisterChannel. If one of the stan‐
106 dard channels, stdin, stdout or stderr was previously closed, the act
107 of creating the new channel also assigns it as a replacement for the
108 standard channel.
109 TCL_MAKETCPCLIENTCHANNEL
111 Tcl_MakeTcpClientChannel creates a Tcl_Channel around an existing,
112 platform specific, handle for a client TCP socket.
113 The newly created channel is not registered in the supplied inter‐
115 preter; to register it, use Tcl_RegisterChannel. If one of the stan‐
116 dard channels, stdin, stdout or stderr was previously closed, the act
117 of creating the new channel also assigns it as a replacement for the
118 standard channel.
119 TCL_OPENTCPSERVER
121 Tcl_OpenTcpServer opens a TCP socket on the local host on a specified
122 port and uses the Tcl event mechanism to accept requests from clients
123 to connect to it. The myaddr argument specifies the network interface.
124 If myaddr is NULL the special address INADDR_ANY should be used to al‐
125 low connections from any network interface. Each time a client con‐
126 nects to this socket, Tcl creates a channel for the new connection and
127 invokes proc with information about the channel. Proc must match the
128 following prototype:
129 typedef void Tcl_TcpAcceptProc(
131 ClientData clientData,
132 Tcl_Channel channel,
133 char *hostName,
134 int port);
135 The clientData argument will be the same as the clientData argument to
137 Tcl_OpenTcpServer, channel will be the handle for the new channel,
138 hostName points to a string containing the name of the client host mak‐
139 ing the connection, and port will contain the client's port number.
140 The new channel is opened for both input and output. If proc raises an
141 error, the connection is closed automatically. Proc has no return
142 value, but if it wishes to reject the connection it can close channel.
143 Tcl_OpenTcpServer normally returns a pointer to a channel representing
145 the server socket. If an error occurs, Tcl_OpenTcpServer returns NULL
146 and records a POSIX error code that can be retrieved with Tcl_GetErrno.
147 In addition, if the interpreter is non-NULL, an error message is left
148 in the interpreter's result.
149 The channel returned by Tcl_OpenTcpServer cannot be used for either in‐
151 put or output. It is simply a handle for the socket used to accept
152 connections. The caller can close the channel to shut down the server
153 and disallow further connections from new clients.
154 TCP server channels operate correctly only in applications that dis‐
156 patch events through Tcl_DoOneEvent or through Tcl commands such as
157 vwait; otherwise Tcl will never notice that a connection request from a
158 remote client is pending.
159 The newly created channel is not registered in the supplied inter‐
161 preter; to register it, use Tcl_RegisterChannel. If one of the stan‐
162 dard channels, stdin, stdout or stderr was previously closed, the act
163 of creating the new channel also assigns it as a replacement for the
164 standard channel.
165
167 On Unix platforms, the socket handle is a Unix file descriptor as re‐
168 turned by the socket system call. On the Windows platform, the socket
169 handle is a SOCKET as defined in the WinSock API.
170
172 Tcl_OpenFileChannel(3), Tcl_RegisterChannel(3), vwait(n)
173
175 channel, client, server, socket, TCP
176Tcl 8.0 Tcl_OpenTcpClient(3)