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官网:http://libevent.org/
1.4和2.x系列版本,1.4 比较老,但源码简单,适合学习;
2.x 比较新,使用时建议用2.x版本,与1.4版本接口不兼容。
当前2个系列版本状态(2020.02.09)
libevent-release-1.4.15-stable.tar.gz
libevent-2.1.11-stable.tar.gz
./configure 检查安装环境,生成makefile
make 生成目标文件和可执行文件
sudo make install 将相关头文件、库文件复制到系统目录
这里以2.11版本为例
解压
tar -zxvf libevent-2.1.11-stable.tar.gz
进入解压后的目录
cd libevent-2.1.11-stable/
./configure #检查安装环境,生成makefile
make #生成目标文件和可执行文件
sudo make install #将相关头文件、库文件复制到系统目录
提示库已经安装到/usr/local/lib
可进入目录查看相关库
另外头文件位于/usr/local/include
其中event2是一个目录,
进入sample目录:
cd sample
$ gcc -o hello hello-world.c -levent
运行demo:
./hello
运行一个客户端连接
$nc 127.0.0.1 9995
客户端连接服务端后,服务端反馈hello,world后,立马进行FIN挥手,客户端进行ACK应答。
使用wireshark抓包查看
大致可以看出监听端口号为9995
事件中交互一个MESSAGE(为字符串"Hello, World!\n";)
/* This example program provides a trivial server program that listens for TCP connections on port 9995. When they arrive, it writes a short message to each client connection, and closes each connection once it is flushed. Where possible, it exits cleanly in response to a SIGINT (ctrl-c). */ #include <string.h> #include <errno.h> #include <stdio.h> #include <signal.h> #ifndef _WIN32 #include <netinet/in.h> # ifdef _XOPEN_SOURCE_EXTENDED # include <arpa/inet.h> # endif #include <sys/socket.h> #endif #include <event2/bufferevent.h> #include <event2/buffer.h> #include <event2/listener.h> #include <event2/util.h> #include <event2/event.h> static const char MESSAGE[] = "Hello, World!\n"; static const int PORT = 9995; static void listener_cb(struct evconnlistener *, evutil_socket_t, struct sockaddr *, int socklen, void *); static void conn_writecb(struct bufferevent *, void *); static void conn_eventcb(struct bufferevent *, short, void *); static void signal_cb(evutil_socket_t, short, void *); int main(int argc, char **argv) { struct event_base *base; struct evconnlistener *listener; struct event *signal_event; struct sockaddr_in sin; #ifdef _WIN32 WSADATA wsa_data; WSAStartup(0x0201, &wsa_data); #endif base = event_base_new(); if (!base) { fprintf(stderr, "Could not initialize libevent!\n"); return 1; } memset(&sin, 0, sizeof(sin)); sin.sin_family = AF_INET; sin.sin_port = htons(PORT); listener = evconnlistener_new_bind(base, listener_cb, (void *)base, LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE, -1, (struct sockaddr*)&sin, sizeof(sin)); if (!listener) { fprintf(stderr, "Could not create a listener!\n"); return 1; } signal_event = evsignal_new(base, SIGINT, signal_cb, (void *)base); if (!signal_event || event_add(signal_event, NULL)<0) { fprintf(stderr, "Could not create/add a signal event!\n"); return 1; } event_base_dispatch(base); evconnlistener_free(listener); event_free(signal_event); event_base_free(base); printf("done\n"); return 0; } static void listener_cb(struct evconnlistener *listener, evutil_socket_t fd, struct sockaddr *sa, int socklen, void *user_data) { struct event_base *base = user_data; struct bufferevent *bev; bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE); if (!bev) { fprintf(stderr, "Error constructing bufferevent!"); event_base_loopbreak(base); return; } bufferevent_setcb(bev, NULL, conn_writecb, conn_eventcb, NULL); bufferevent_enable(bev, EV_WRITE); bufferevent_disable(bev, EV_READ); bufferevent_write(bev, MESSAGE, strlen(MESSAGE)); } static void conn_writecb(struct bufferevent *bev, void *user_data) { struct evbuffer *output = bufferevent_get_output(bev); if (evbuffer_get_length(output) == 0) { printf("flushed answer\n"); bufferevent_free(bev); } } static void conn_eventcb(struct bufferevent *bev, short events, void *user_data) { if (events & BEV_EVENT_EOF) { printf("Connection closed.\n"); } else if (events & BEV_EVENT_ERROR) { printf("Got an error on the connection: %s\n", strerror(errno));/*XXX win32*/ } /* None of the other events can happen here, since we haven't enabled * timeouts */ bufferevent_free(bev); } static void signal_cb(evutil_socket_t sig, short events, void *user_data) { struct event_base *base = user_data; struct timeval delay = { 2, 0 }; printf("Caught an interrupt signal; exiting cleanly in two seconds.\n"); event_base_loopexit(base, &delay); }
功能:netcat的简写,是一个简单而有用的工具。可以作为各种TCP和UDP监听和连接测试用途。
可用参数
$ nc -help
OpenBSD netcat (Debian patchlevel 1.187-1ubuntu0.1)
usage: nc [-46CDdFhklNnrStUuvZz] [-I length] [-i interval] [-M ttl]
[-m minttl] [-O length] [-P proxy_username] [-p source_port]
[-q seconds] [-s source] [-T keyword] [-V rtable] [-W recvlimit] [-w timeout]
[-X proxy_protocol] [-x proxy_address[:port]] [destination] [port]
Command Summary:
-4 Use IPv4
-6 Use IPv6
-b Allow broadcast
-C Send CRLF as line-ending
-D Enable the debug socket option
-d Detach from stdin
-F Pass socket fd
-h This help text
-I length TCP receive buffer length
-i interval Delay interval for lines sent, ports scanned
-k Keep inbound sockets open for multiple connects
-l Listen mode, for inbound connects
-M ttl Outgoing TTL / Hop Limit
-m minttl Minimum incoming TTL / Hop Limit
-N Shutdown the network socket after EOF on stdin
-n Suppress name/port resolutions
-O length TCP send buffer length
-P proxyuser Username for proxy authentication
-p port Specify local port for remote connects
-q secs quit after EOF on stdin and delay of secs
-r Randomize remote ports
-S Enable the TCP MD5 signature option
-s source Local source address
-T keyword TOS value
-t Answer TELNET negotiation
-U Use UNIX domain socket
-u UDP mode
-V rtable Specify alternate routing table
-v Verbose
-W recvlimit Terminate after receiving a number of packets
-w timeout Timeout for connects and final net reads
-X proto Proxy protocol: “4”, “5” (SOCKS) or “connect”
-x addr[:port] Specify proxy address and port
-Z DCCP mode
-z Zero-I/O mode [used for scanning]
Port numbers can be individual or ranges: lo-hi [inclusive]
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