融合libevent和protobuf
写了一个简单的例子，把libevent中的bufferevent网络收发服务和protobuf里面的序列反序列结合起来。
protobuf文件message.proto：
message PMessage { required int32 id = 1; optional int32 num = 2; optional string str = 3; }
生成接口命令：
protoc -I=proto --cpp_out=src proto/message.proto
服务器端 lserver.cc：
#include <netinet/in.h> #include <sys/socket.h> #include <unistd.h> #include <stdio.h> #include <string.h> #include <event.h> #include <event2/listener.h> #include <event2/bufferevent.h> #include <event2/thread.h> #include "message.pb.h" using namespace std; void listener_cb(evconnlistener *listener, evutil_socket_t fd, sockaddr *sock, int socklen, void *arg); void socket_read_cb(bufferevent *bev, void *arg); void socket_event_cb(bufferevent *bev, short events, void *arg); int main(int argc, char **argv) { sockaddr_in sin; memset(&sin, 0, sizeof(sockaddr_in)); sin.sin_family = AF_INET; sin.sin_port = htons(8899); event_base *base = event_base_new(); evconnlistener *listener = evconnlistener_new_bind(base, listener_cb, base, LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE, 10, (sockaddr*)&sin, sizeof(sockaddr_in)); event_base_dispatch(base); evconnlistener_free(listener); event_base_free(base); } void listener_cb(evconnlistener *listener, evutil_socket_t fd, sockaddr *sock, int socklen, void *arg) { printf("accept a client %d\n", fd); event_base *base = (event_base *)arg; bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE); bufferevent_setcb(bev, socket_read_cb, NULL, socket_event_cb, NULL); bufferevent_enable(bev, EV_READ|EV_PERSIST); } void socket_read_cb(bufferevent *bev, void *arg) { char msg[4096]; size_t len = bufferevent_read(bev, msg, sizeof(msg)-1); msg[len] = '\0'; PMessage pmsg; pmsg.ParseFromArray((const void*)msg, len); printf("Server read the data:%i, %i, %s\n", pmsg.id(), pmsg.num(), pmsg.str().c_str()); pmsg.set_str("I have read your data."); string sendbuf; pmsg.SerializeToString(&sendbuf); bufferevent_write(bev, sendbuf.c_str(), sendbuf.length()); } void socket_event_cb(bufferevent *bev, short events, void *arg) { if (events & BEV_EVENT_EOF) { printf("connection close\n"); } else if (events & BEV_EVENT_ERROR) { printf("some other error\n"); } bufferevent_free(bev); }
客户端lclient.cc
#include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <errno.h> #include <unistd.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #include <event.h> #include <event2/bufferevent.h> #include <event2/buffer.h> #include <event2/util.h> #include "message.pb.h" using namespace std; void cmd_msg_cb(int fd, short events, void *arg); void server_msg_cb(bufferevent *bev, void *arg); void event_cb(bufferevent *bev, short event, void *arg); static int gid = 1; int main(int argc, char **argv) { if (argc < 3) { printf("please input IP and port\n"); return 1; } event_base *base = event_base_new(); bufferevent *bev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE); event *ev_cmd = event_new(base, STDIN_FILENO, EV_READ|EV_PERSIST, cmd_msg_cb, (void *)bev); event_add(ev_cmd, NULL); sockaddr_in server_addr; memset(&server_addr, 0, sizeof(server_addr)); server_addr.sin_family = AF_INET; server_addr.sin_port = htons(atoi(argv[2])); inet_aton(argv[1], &server_addr.sin_addr); bufferevent_socket_connect(bev, (sockaddr*)&server_addr, sizeof(server_addr)); bufferevent_setcb(bev, server_msg_cb, NULL, event_cb, (void*)ev_cmd); bufferevent_enable(bev, EV_READ|EV_PERSIST); event_base_dispatch(base); printf("Finish\n"); return 0; } void cmd_msg_cb(int fd, short events, void *arg) { char msg[1024]; int ret = read(fd, msg, sizeof(msg)); if (ret < 0) { perror("read error.\n"); exit(1); } // protobuf PMessage pmsg; pmsg.set_id(gid++); pmsg.set_num(rand()); pmsg.set_str(msg); string sendbuf; pmsg.SerializeToString(&sendbuf); // processing network transfer bufferevent *bev = (bufferevent *)arg; bufferevent_write(bev, sendbuf.c_str(), sendbuf.length()); } void server_msg_cb(bufferevent *bev, void *arg) { char msg[1024]; size_t len = bufferevent_read(bev, msg, sizeof(msg)-1); msg[len] = '\0'; PMessage pmsg; pmsg.ParseFromArray((const void*)msg, len); printf("Recv %d, %d, %s from server.\n", pmsg.id(), pmsg.num(), pmsg.str().c_str()); } void event_cb(bufferevent *bev, short eventid, void *arg) { if (eventid & BEV_EVENT_EOF) { printf("Connection closed.\n"); } else if (eventid & BEV_EVENT_ERROR) { printf("Some other error.\n"); } else if (eventid & BEV_EVENT_CONNECTED) { printf("Client has successfully connected.\n"); return; } bufferevent_free(bev); event *ev = (event *)arg; event_free(ev); }
服务器端和客户端共用的Makefile：
CXX=/opt/compiler/gcc-4.8.2/bin/g++ INCPATH= \ /home/work/.jumbo/include/ DEP_LDFLAGS= \ -L/home/work/.jumbo/lib/ DEP_LDLIBS= \ -levent \ -lprotobuf \ -lpthread TARGET= lserver lclient all : $(TARGET) lserver : lserver.cc message.pb.cc $(CXX) -o $@ $^ -I$(INCPATH) $(DEP_LDFLAGS) $(DEP_LDLIBS) lclient : lclient.cc message.pb.cc $(CXX) -o $@ $^ -I$(INCPATH) $(DEP_LDFLAGS) $(DEP_LDLIBS) .PHONY : all clean clean : rm -rf $(TARGET)
服务器命令及输出：
src]$ ./lserver accept a client 7 Server read the data:1, 1804289383, aaaaaaaaaaaaaaaaaaaaaaaaa Server read the data:2, 846930886, aa Server read the data:3, 1681692777, bb Server read the data:4, 1714636915, abcdefg Server read the data:5, 1957747793, connection close accept a client 7 Server read the data:1, 1804289383, 2aa Server read the data:2, 846930886, 2bb Server read the data:3, 1681692777, 111111111111111111111222222222222222222222223333333333333333333333333 Server read the data:4, 1714636915, ^C
客户端命令及输出：
src]$ ./lclient localhost 8899 Client has successfully connected. aaaaaaaaaaaaaaaaaaaaaaaaa Recv 1, 1804289383, I have read your data. from server. aa Recv 2, 846930886, I have read your data. from server. bb Recv 3, 1681692777, I have read your data. from server. abcdefg Recv 4, 1714636915, I have read your data. from server. Recv 5, 1957747793, I have read your data. from server. ^C [src]$ ./lclient localhost 8899 Client has successfully connected. 2aa Recv 1, 1804289383, I have read your data. from server. 2bb Recv 2, 846930886, I have read your data. from server. 111111111111111111111222222222222222222222223333333333333333333333333 Recv 3, 1681692777, I have read your data. from server. Recv 4, 1714636915, I have read your data. from server. Connection closed. Finish
注意：
1. 先后开了两个客户端。客户端退出，不影响服务器端。但是服务器端退出会让客户端一起退出，因为客户端在收到网络error信号处理的最后，会free掉从命令行读数据的监听event，这样eventbase就不会再有event需要监听了，所以会退出。
2. 开始在命令行输入的时候，在char数组中没有添加'\0'，传输时会造成如下错误。
[libprotobuf ERROR google/protobuf/wire_format.cc:1053] String field contains invalid UTF-8 data when serializing a protocol buffer. Use the 'bytes' type if you intend to send raw bytes.
根据读入函数返回的长度，设置'\0'即可避免这个错误。
