libcurl delays for 1 second before uploading data, command-line curl does not
c, curl, libcurl, mongoose-web-server
Solution
The reason for the delay was:
- libcurl was sending an `Expect: 100-Continue` header
- The server (which is based on mongoose) is not configured to send `100 Continue` responses automatically.
- libcurl waits up to 1 second for this response. If it does not receive it after this time then it proceeds to send the request body anyway.
A solution on the client side is to disable the `Expect` header like so:
headers = curl_slist_append(NULL, "Expect:");
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
// ...
result = curl_easy_perform(curl);
curl_slist_free_all(headers);
Equivalent fix for PHP client and related PHP question
Problem
I am using libcurl to send an API command to a local service (i.e. on 127.0.0.1). The program is intended to replace a shell script (that uses the `curl` program.) Everything is working, except that there is a 1-second delay somewhere, i.e 1 second elapses from the time I call `curl_easy_perform()` to when my read callback function is first called. The C program is using these options (error checking & callback code omitted): ``` curl_easy_setopt(curl, CURLOPT_URL, "http://127.0.0.1:12345/x"); curl_easy_setopt(curl, CURLOPT_UPLOAD, 1); curl_easy_setopt(curl, CURLOPT_INFILESIZE, (long)getLengthOfCommandObject()); curl_easy_setopt(curl, CURLOPT_READFUNCTION, &myReadFunction); curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, &myWriteFunction); ``` But if I run `curl` from the shell like this: ``` $ curl --data-binary '<command>' http://127.0.0.1:12345/x ``` it sends the request immediately, without suffering from the 1-second delay. What might be causing the delay, and is there an option I can set to prevent it? Edit The server is based on mongoose