136 lines
4.1 KiB
Markdown
136 lines
4.1 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: curl_ws_send
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Section: 3
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Source: libcurl
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See-also:
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- curl_easy_getinfo (3)
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- curl_easy_perform (3)
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- curl_easy_setopt (3)
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- curl_ws_recv (3)
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- libcurl-ws (3)
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Protocol:
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- WS
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Added-in: 7.86.0
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---
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# NAME
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curl_ws_send - send WebSocket data
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLcode curl_ws_send(CURL *curl, const void *buffer, size_t buflen,
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size_t *sent, curl_off_t fragsize,
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unsigned int flags);
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~~~
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# DESCRIPTION
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Send the specific message chunk over an established WebSocket
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connection. *buffer* must point to a valid memory location containing
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(at least) *buflen* bytes of payload memory.
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*sent* is set to the number of payload bytes actually sent. If the return value
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is **CURLE_OK** but *sent* is less than the given *buflen*, libcurl was unable
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to consume the complete payload in a single call. In this case the application
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must call this function again until all payload is processed. *buffer* and
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*buflen* must be updated on every following invocation to only point to the
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remaining piece of the payload.
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*fragsize* should always be set to zero unless a (huge) frame shall be sent
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using multiple calls with partial content per call explicitly. In that
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case you must set the *CURLWS_OFFSET* bit and set the *fragsize* as documented
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in the section on *CURLWS_OFFSET* below.
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*flags* must contain at least one flag indicating the type of the message.
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To send a fragmented message consisting of multiple frames, additionally set
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the *CURLWS_CONT* bit in all frames except the final one. The appropriate
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message type bit should be set in every frame of a fragmented message without
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exemption. Omitting the message type for continuation frames of a fragmented
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message is only supported for backwards compatibility and highly discouraged.
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For more details on the supported flags see below and in curl_ws_meta(3).
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If *CURLWS_RAW_MODE* is enabled in CURLOPT_WS_OPTIONS(3), the
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*flags* argument should be set to 0.
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Warning: while it is possible to invoke this function from a callback,
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such a call is blocking in this situation, e.g. only returns after all data
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has been sent or an error is encountered.
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# FLAGS
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Supports all flags documented in curl_ws_meta(3) and additionally the following
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flags.
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## CURLWS_OFFSET
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The provided data is only a partial frame and there is more coming in a
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following call to *curl_ws_send()*. When sending only a piece of the
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frame like this, the *fragsize* must be provided with the total
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expected frame size in the first call and must be zero in all subsequent
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calls.
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# %PROTOCOLS%
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# EXAMPLE
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~~~c
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#include <string.h> /* for strlen */
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int main(void)
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{
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const char *buffer = "PAYLOAD";
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size_t offset = 0;
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CURLcode res = CURLE_OK;
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CURL *curl = curl_easy_init();
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curl_easy_setopt(curl, CURLOPT_URL, "wss://example.com/");
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curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 2L);
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/* start HTTPS connection and upgrade to WSS, then return control */
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curl_easy_perform(curl);
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while(!res) {
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size_t sent;
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res = curl_ws_send(curl, buffer + offset, strlen(buffer) - offset, &sent,
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0, CURLWS_TEXT);
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offset += sent;
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if(res == CURLE_OK) {
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if(offset == strlen(buffer))
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break; /* finished sending */
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}
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if(res == CURLE_AGAIN)
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/* in real application: wait for socket here, e.g. using select() */
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res = CURLE_OK;
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}
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curl_easy_cleanup(curl);
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return (int)res;
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}
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~~~
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# %AVAILABILITY%
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# RETURN VALUE
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This function returns a CURLcode indicating success or error.
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CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
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libcurl-errors(3). If CURLOPT_ERRORBUFFER(3) was set with curl_easy_setopt(3)
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there can be an error message stored in the error buffer when non-zero is
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returned.
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Instead of blocking, the function returns **CURLE_AGAIN**. The correct
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behavior is then to wait for the socket to signal readability before calling
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this function again.
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Any other non-zero return value indicates an error. See the libcurl-errors(3)
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man page for the full list with descriptions.
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