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。