About the use of tcp_echo_client.c and tcp_echo_server.p

[illidanstormrange]

Hello！

When I run tcp_echo_client.c, I cannot connect to the server run by tcp_echo_server.py. The server can print the connection request, but emscripten_websocket_get_ready_state always returns 0, and the connection cannot be established correctly.

Does it mean that as a bridge, it can only connect to the websocket server, but not to TCP? Then why does your sample code have both websocket connection and connect(socket)? If you see this, please help me solve my doubts. Thank you.

I used cmake to compile, here is my CMake

cmake_minimum_required(VERSION 3.6)
project(test_main)
set(LIBRARY_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/lib)
set(CMAKE_CXX_STANDARD 11)

if (DEFINED EMSCRIPTEN)
    list(APPEND LINK_OPTIONS -sWASM=1 -sPROXY_POSIX_SOCKETS=1 -lwebsocket.js -sUSE_PTHREADS=1)
    # list(APPEND LINK_OPTIONS -sWASM=1)
endif ()

set(CMAKE_EXECUTABLE_SUFFIX ".html") # 编译生成.html

add_executable(test_main test_emscripten.cpp)
target_link_options(test_main PUBLIC ${LINK_OPTIONS})

[sbc100]

Does it mean that as a bridge, it can only connect to the websocket server, but not to TCP? Then why does your sample code have both websocket connection and connect(socket)? If you see this, please help me solve my doubts. Thank you.

I'll try to answer this question specifically: When you use PROXY_POSIX_SOCKETS all socket communication (i.e. all TCP/UDP connections from the C/C++ code) are proxied (i.e. tunneled) through a single websocket connection that you need to run on your server.

On one of the websocket is you web application, on the other end (i.e. on your web server) you need run a proxying server. The source code for this is here: https://github.com/emscripten-core/emscripten/tree/main/tools/websocket_to_posix_proxy

See https://emscripten.org/docs/porting/networking.html#full-posix-sockets-over-websocket-proxy-server

[illidanstormrange]

Thank you for your reply. I found the previous problem after reading this code.
But i ran the proxy server and tried to connect using tcp_echo_client,unfortunately, I got the same result. emscripten_websocket_get_ready_state always returned 0. When I checked ws through the browser, it did not receive the handshake successfully.

[illidanstormrange]

When I create a websocket client with the following code, it can receive the handshake, but there will be a connection problem

#include <emscripten.h>
#include <emscripten/websocket.h>
#include <stdio.h>
 
EM_BOOL onopen(int eventType, const EmscriptenWebSocketOpenEvent *websocketEvent, void *userData) {
    puts("onopen");
    EMSCRIPTEN_RESULT result = emscripten_websocket_send_utf8_text(websocketEvent->socket, "hello world");
    if (result) {
        printf("Failed to emscripten_websocket_send_utf8_text(): %d\n", result);
    }
    return EM_TRUE;
}
 
EM_BOOL onerror(int eventType, const EmscriptenWebSocketErrorEvent *websocketEvent, void *userData) {
    puts("onerror");
    return EM_TRUE;
}
 
EM_BOOL onclose(int eventType, const EmscriptenWebSocketCloseEvent *websocketEvent, void *userData) {
    puts("onclose");
    return EM_TRUE;
}
 
EM_BOOL onmessage(int eventType, const EmscriptenWebSocketMessageEvent *websocketEvent, void *userData) {
    puts("onmessage");
    if (websocketEvent->isText) {
        printf("message: %s\n", websocketEvent->data);
    }
    EMSCRIPTEN_RESULT result = emscripten_websocket_close(websocketEvent->socket, 1000, "no reason");
    if (result) {
        printf("Failed to emscripten_websocket_close(): %d\n", result);
    }
    return EM_TRUE;
}
 
int main() {
    if (!emscripten_websocket_is_supported()) {
        return 0;
    }
 
    EmscriptenWebSocketCreateAttributes ws_attrs = {"ws://localhost:8080", NULL, EM_TRUE};
    EMSCRIPTEN_WEBSOCKET_T ws = emscripten_websocket_new(&ws_attrs);
 
    emscripten_websocket_set_onopen_callback(ws, NULL, onopen);
    emscripten_websocket_set_onerror_callback(ws, NULL, onerror);
    emscripten_websocket_set_onclose_callback(ws, NULL, onclose);
    emscripten_websocket_set_onmessage_callback(ws, NULL, onmessage);
 
    return 0;
}

I can see in the browser that the ws connection has been established