ReceiveString Returns Only the Immediately Available Data

See more Socket/SSL/TLS Examples

Demonstrates that Socket.ReceiveString returns only the text immediately available and not the entire response. The example connects to chilkatsoft.com over TLS and requests big_helloWorld.txt, a large text file of roughly 74,000 lines. A single ReceiveString call returns just the first portion of the response, and the example reports how many characters were received compared with the total size given by the response Content-Length header.

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    const socket = try chilkat.Socket.init();
    defer socket.deinit();

    // Connect to chilkatsoft.com over TLS.
    const b_tls = true;
    const max_wait_ms = 5000;
    socket.connect("chilkatsoft.com", 443, b_tls, max_wait_ms) catch {
        std.debug.print("{s}\n", .{try socket.getLastErrorText(alloc)});
        return;
    };

    socket.setStringCharset("utf-8");

    // Send an HTTP GET request for big_helloWorld.txt, a large text file of roughly 74,000 lines of
    // "Hello World!".  This uses a minimal HTTP request only to exercise ReceiveString against a public
    // server -- for real HTTP work, use the Chilkat Http, Rest, or HttpCurl classes instead.
    const http_req = "GET /big_helloWorld.txt HTTP/1.1\r\nHost: chilkatsoft.com\r\nConnection: close\r\n\r\n";
    socket.sendString(http_req) catch {
        std.debug.print("{s}\n", .{try socket.getLastErrorText(alloc)});
        return;
    };

    // Call ReceiveString a single time.  It returns only the text that is immediately available --
    // typically just the first network packet -- and does NOT wait for the entire response to arrive.
    const response_text = socket.receiveString(alloc) catch {
        std.debug.print("{s}\n", .{try socket.getLastErrorText(alloc)});
        return;
    };

    // Load the received text into a StringBuilder so its length can be measured and the Content-Length
    // header extracted.  The Content-Length header gives the total size, in bytes, of the response body.
    const sb = try chilkat.StringBuilder.init();
    defer sb.deinit();
    sb.append(response_text) catch {};
    const content_length = sb.getBetween(alloc, "Content-Length: ", "\r\n") catch {
        std.debug.print("{s}\n", .{try sb.getLastErrorText(alloc)});
        return;
    };

    // Compare what this single ReceiveString returned against the full size of the expected response.
    // The received amount is only a small fraction of the total.
    std.debug.print("Characters received so far (headers + partial body): {d}\n", .{sb.getLength()});
    std.debug.print("Expected response body size (Content-Length): {s} bytes\n", .{content_length});

    // A single ReceiveString call returns whatever is currently available, so it cannot indicate whether
    // the full response has arrived.  This makes it difficult to know when a response is complete: the
    // application must either know how many bytes to expect (for example from a Content-Length header or
    // an application-defined length prefix) and keep receiving until that many bytes are collected, or
    // keep receiving until the peer closes the connection.
}