Boost-ASIO simple echo client-server cannot establish connection?

问题

I'm using BOOST-ASIO for a simple echo client-server (there is a separate link for the client and server). When I try to run the server I use this async_tcp_echo_server 4000. For the client I use blocking_tcp_echo_client #.#.#.# 4000 (with #.#.#.# as the ip address). I'm on XP-SP3 with my computer connected to my wireless dsl modem using a usb card. After a few seconds on the client side I get this error:

Exception: connect: A connection attempt failed because the connected party did
not properly respond after a period of time, or established connection failed be
cause connected host has failed to respond

Any ideas what it could be? I turned off my firewall including the windows firewall and still I get no response. Could my port be in the incorrect range? Do I need to include a computer name to specify the machine on the network( there are other machines on the network sometimes active)? I did try running this on another computer directly connected to the dsl modem and same issue. I did ping my address and that did work for 4/4 packets.

回答1:

It could be a variety of issues. Thus, it can be worthwhile to use lower level networking tools, such as netcat to serve a port on the server, and try connecting with netcat from the client side. This can help simplify the problem by removing any potential problems introduced by an application's network programming code. If the problem is identified as being a network issue, then there are a few things to check:

• Verify firewall exceptions on the server.
• Verify firewall exceptions in the server's network gateway.
• If the server and client are on different networks, with the client trying to connect to the server's external IP, then verify that the server's gateway knows what traffic to route to the server. This may require setting up rules, such as port forwarding, in the routing device.
• If the server and client are on the same network, but the client is trying to connect to the server through the network's external IP, then verify that the gateway supports looping back internal traffic destined to the external IP.
• Use a network analyzer tool, such as Wireshark, to verify that the time to live field in the packets is high enough that it will not be discarded.

回答2:

you could try

$ telnet server-ip 4000

from your client and see if it is possible to establish the tcp connection.

来源：https://stackoverflow.com/questions/15035824/boost-asio-simple-echo-client-server-cannot-establish-connection