原文作者:http://www.cnblogs.com/lianyue
这一部分需要向大家介绍的是服务器的select以及收发包的具体流程，从核心代码功能上分析网络交互具体过程。
首先大家要看第二部分（part2 of net）的代码结构图，因为在接下来的流程过程中会用到其中模块的名称，若是不知道大致的功能那么接下来的解说可能就成为天书了。
总体流程为：服务器管理器初始化并创建主套接字连接，进入主循环等待新连接（select），如果有新的连接则将新连接加入连接管理器。不管有没有新的连接，循环会依次处理连接的异常->输入流->输出流->命令处理。其中异常即连接包发送错误的处理，输入流即套接字输入流中如果大小长度不为空则重新拼接包，输出流进行包的拼接，并将未发送的流进行发送，命令处理其实是对输入流的处理，处理（handler）发送过来的包。
以下详细说明这几个流程从代码上的实现，以及所在的模块。
1、 服务器管理器初始化（servermanager）
bool ServerManager::init() {
__ENTER_FUNCTION
serversocket_ =
new pap_server_common_net::Socket(g_config.billing_info_.port_);
Assert(serversocket_);
serversocket_->set_nonblocking();
socketid_ = serversocket_->getid();
Assert(socketid_ != SOCKET_INVALID);
FD_SET(socketid_, &readfds_[kSelectFull]);
FD_SET(socketid_, &exceptfds_[kSelectFull]);
minfd_ = maxfd_ = socketid_;
timeout_[kSelectFull].tv_sec = 0;
timeout_[kSelectFull].tv_usec = 0;
threadid_ = pap_common_sys::get_current_thread_id();
uint16_t i;
for (i = 0; i < OVER_SERVER_MAX; ++i) {
serverhash_[i] = ID_INVALID;
}
return true;
__LEAVE_FUNCTION
return false;
}
2、 服务器管理器进入主循环（servermanager）
void ServerManager::loop() {
__ENTER_FUNCTION
while (isactive()) {
bool result = false;
try {
result = select();
Assert(result);
//ERRORPRINTF("select");
result = processexception();
Assert(result);
//ERRORPRINTF("processexception");
result = processinput();
Assert(result);
//ERRORPRINTF("processinput");
result = processoutput();
Assert(result);
//ERRORPRINTF("processoutput");
}
catch(...) {
}
try {
result = processcommand();
Assert(result);
//ERRORPRINTF("processcommand");
}
catch(...) {
}
try {
result = heartbeat();
Assert(result);
}
catch(...) {
}
}
__LEAVE_FUNCTION
}
3、 服务器线程进入select模式
bool ServerManager::select() {
__ENTER_FUNCTION
timeout_[kSelectUse].tv_sec = timeout_[kSelectFull].tv_sec;
timeout_[kSelectUse].tv_usec = timeout_[kSelectFull].tv_usec;
readfds_[kSelectUse] = readfds_[kSelectFull];
writefds_[kSelectUse] = writefds_[kSelectFull];
exceptfds_[kSelectUse] = exceptfds_[kSelectFull];
pap_common_base::util::sleep(100);
int32_t result = SOCKET_ERROR;
try {
result = pap_common_net::socket::Base::select(
maxfd_ + 1,
&readfds_[kSelectUse],
&writefds_[kSelectUse],
&exceptfds_[kSelectUse],
&timeout_[kSelectUse]);
Assert(result != SOCKET_ERROR);
}
catch(...) {
g_log->fast_save_log(kBillingLogFile,
"ServerManager::select have error, result: %d",
result);
}
return true;
__LEAVE_FUNCTION
return false;
}
4、 服务器线程进行异常处理
bool ServerManager::processexception() {
__ENTER_FUNCTION
if (SOCKET_INVALID == minfd_ && SOCKET_INVALID == maxfd_)
return true;
uint16_t connectioncount = billingconnection::Manager::getcount();
billingconnection::Server* serverconnection = NULL;
uint16_t i;
for (i = 0; i < connectioncount; ++i) {
if (ID_INVALID == connectionids_[i]) continue;
serverconnection = g_connectionpool->get(connectionids_[i]);
Assert(serverconnection);
int32_t socketid = serverconnection->getsocket()->getid();
if (socketid_ == socketid) {
Assert(false);
continue;
}
if (FD_ISSET(socketid, &exceptfds_[kSelectUse])) {
removeconnection(serverconnection);
}
}
return true;
__LEAVE_FUNCTION
return false;
}
5、 服务器线程进行输入流处理
bool ServerManager::processinput() {
__ENTER_FUNCTION
if (SOCKET_INVALID == minfd_ && SOCKET_INVALID == maxfd_)
return true; //no connection
uint16_t i;
if (FD_ISSET(socketid_, &readfds_[kSelectUse])) {
for (i = 0; i < kOneStepAccept; ++i) {
if (!accept_newconnection()) break;
}
}
uint16_t connectioncount = billingconnection::Manager::getcount();
for (i = 0; i < connectioncount; ++i) {
if (ID_INVALID == connectionids_[i]) continue;
billingconnection::Server* serverconnection = NULL;
serverconnection = g_connectionpool->get(connectionids_[i]);
Assert(serverconnection);
int32_t socketid = serverconnection->getsocket()->getid();
if (socketid_ == socketid) continue;
if (FD_ISSET(socketid, &readfds_[kSelectUse])) { //read information
if (serverconnection->getsocket()->iserror()) {
removeconnection(serverconnection);
}
else {
try {
if (!serverconnection->processinput())
removeconnection(serverconnection);
}
catch(...) {
removeconnection(serverconnection);
}
}
}
}
return true;
__LEAVE_FUNCTION
return false;
}
6、 服务器线程进行输出流处理
bool ServerManager::processoutput() {
__ENTER_FUNCTION
if (SOCKET_INVALID == maxfd_&& SOCKET_INVALID == minfd_)
return false;
uint16_t i;
uint16_t connectioncount = billingconnection::Manager::getcount();
for (i = 0; i < connectioncount; ++i) {
if (ID_INVALID == connectionids_[i]) continue;
billingconnection::Server* serverconnection = NULL;
serverconnection = g_connectionpool->get(connectionids_[i]);
Assert(serverconnection);
int32_t socketid = serverconnection->getsocket()->getid();
if (socketid_ == socketid) continue;
if (FD_ISSET(socketid, &writefds_[kSelectUse])) {
if (serverconnection->getsocket()->iserror()) {
removeconnection(serverconnection);
}
else {
try {
if (!serverconnection->processoutput())
removeconnection(serverconnection);
}
catch(...) {
removeconnection(serverconnection);
}
}
}
}
return true;
__LEAVE_FUNCTION
return false;
}
7、 服务器线程进行命令处理
bool ServerManager::processcommand() {
__ENTER_FUNCTION
if (SOCKET_INVALID == maxfd_&& SOCKET_INVALID == minfd_)
return false;
uint16_t i;
uint16_t connectioncount = billingconnection::Manager::getcount();
for (i = 0; i < connectioncount; ++i) {
if (ID_INVALID == connectionids_[i]) continue;
billingconnection::Server* serverconnection = NULL;
serverconnection = g_connectionpool->get(connectionids_[i]);
//serverconnection = &billing_serverconnection_;
Assert(serverconnection);
int32_t socketid = serverconnection->getsocket()->getid();
if (socketid_ == socketid) continue;
if (serverconnection->getsocket()->iserror()) {
removeconnection(serverconnection);
}
else { //connection is ok
try {
if (!serverconnection->processcommand(false))
removeconnection(serverconnection);
}
catch(...) {
removeconnection(serverconnection);
}
}
}
return true;
__LEAVE_FUNCTION
return false;
}
下一部分，我将讲解在网络部分一些重要的代码块。
