1.Socket封装

（1）Endian.h

封装了字节序转换函数（全局函数，位于muduo::net::sockets名称空间中）。

（2）SocketsOps.h/ SocketsOps.cc

封装了socket相关系统调用（全局函数，位于muduo::net::sockets名称空间中）。

（3）Socket.h/Socket.cc（Socket类）

用RAII方法封装socket file descriptor

（4）InetAddress.h/InetAddress.cc（InetAddress类）

网际地址sockaddr_in封装

2.代码

1.SocketsOps.h

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)
//
// This is an internal header file, you should not include this.

#ifndef MUDUO_NET_SOCKETSOPS_H
#define MUDUO_NET_SOCKETSOPS_H

#include <arpa/inet.h>

namespace muduo
{
namespace net
{
namespace sockets
{

///
/// Creates a non-blocking socket file descriptor,
/// abort if any error.
int createNonblockingOrDie();

int  connect(int sockfd, const struct sockaddr_in& addr);
void bindOrDie(int sockfd, const struct sockaddr_in& addr);
void listenOrDie(int sockfd);
int  accept(int sockfd, struct sockaddr_in* addr);
ssize_t read(int sockfd, void *buf, size_t count);
ssize_t readv(int sockfd, const struct iovec *iov, int iovcnt);
ssize_t write(int sockfd, const void *buf, size_t count);
void close(int sockfd);
void shutdownWrite(int sockfd);

void toIpPort(char* buf, size_t size,
              const struct sockaddr_in& addr);
void toIp(char* buf, size_t size,
          const struct sockaddr_in& addr);
void fromIpPort(const char* ip, uint16_t port,
                  struct sockaddr_in* addr);

int getSocketError(int sockfd);

struct sockaddr_in getLocalAddr(int sockfd);
struct sockaddr_in getPeerAddr(int sockfd);
bool isSelfConnect(int sockfd);

}
}
}

#endif  // MUDUO_NET_SOCKETSOPS_H

2.SocketsOps.cc

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)

#include <muduo/net/SocketsOps.h>

#include <muduo/base/Logging.h>
#include <muduo/base/Types.h>
#include <muduo/net/Endian.h>

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>  // snprintf
#include <strings.h>  // bzero
#include <sys/socket.h>
#include <unistd.h>

using namespace muduo;
using namespace muduo::net;

namespace
{

typedef struct sockaddr SA;

const SA* sockaddr_cast(const struct sockaddr_in* addr)
{
  return static_cast<const SA*>(implicit_cast<const void*>(addr));
}

SA* sockaddr_cast(struct sockaddr_in* addr)
{
  return static_cast<SA*>(implicit_cast<void*>(addr));
}

void setNonBlockAndCloseOnExec(int sockfd)
{
  // non-block
  int flags = ::fcntl(sockfd, F_GETFL, 0);
  flags |= O_NONBLOCK;
  int ret = ::fcntl(sockfd, F_SETFL, flags);
  // FIXME check

  // close-on-exec
  flags = ::fcntl(sockfd, F_GETFD, 0);
  flags |= FD_CLOEXEC;
  ret = ::fcntl(sockfd, F_SETFD, flags);
  // FIXME check

  (void)ret;
}

}

int sockets::createNonblockingOrDie()
{
  // socket
#if VALGRIND
  int sockfd = ::socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  if (sockfd < 0)
  {
    LOG_SYSFATAL << "sockets::createNonblockingOrDie";
  }

  setNonBlockAndCloseOnExec(sockfd);
#else
  // Linux 2.6.27以上的内核支持SOCK_NONBLOCK与SOCK_CLOEXEC
  int sockfd = ::socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, IPPROTO_TCP);
  if (sockfd < 0)
  {
    LOG_SYSFATAL << "sockets::createNonblockingOrDie";
  }
#endif
  return sockfd;
}

void sockets::bindOrDie(int sockfd, const struct sockaddr_in& addr)
{
  int ret = ::bind(sockfd, sockaddr_cast(&addr), sizeof addr);
  if (ret < 0)
  {
    LOG_SYSFATAL << "sockets::bindOrDie";
  }
}

void sockets::listenOrDie(int sockfd)
{
  int ret = ::listen(sockfd, SOMAXCONN);
  if (ret < 0)
  {
    LOG_SYSFATAL << "sockets::listenOrDie";
  }
}

int sockets::accept(int sockfd, struct sockaddr_in* addr)
{
  socklen_t addrlen = sizeof *addr;
#if VALGRIND
  int connfd = ::accept(sockfd, sockaddr_cast(addr), &addrlen);
  setNonBlockAndCloseOnExec(connfd);
#else
  int connfd = ::accept4(sockfd, sockaddr_cast(addr),
                         &addrlen, SOCK_NONBLOCK | SOCK_CLOEXEC);
#endif
  if (connfd < 0)
  {
    int savedErrno = errno;
    LOG_SYSERR << "Socket::accept";
    switch (savedErrno)
    {
      case EAGAIN:
      case ECONNABORTED:
      case EINTR:
      case EPROTO: // ???
      case EPERM:
      case EMFILE: // per-process lmit of open file desctiptor ???
        // expected errors
        errno = savedErrno;
        break;
      case EBADF:
      case EFAULT:
      case EINVAL:
      case ENFILE:
      case ENOBUFS:
      case ENOMEM:
      case ENOTSOCK:
      case EOPNOTSUPP:
        // unexpected errors
        LOG_FATAL << "unexpected error of ::accept " << savedErrno;
        break;
      default:
        LOG_FATAL << "unknown error of ::accept " << savedErrno;
        break;
    }
  }
  return connfd;
}

int sockets::connect(int sockfd, const struct sockaddr_in& addr)
{
  return ::connect(sockfd, sockaddr_cast(&addr), sizeof addr);
}

ssize_t sockets::read(int sockfd, void *buf, size_t count)
{
  return ::read(sockfd, buf, count);
}

// readv与read不同之处在于，接收的数据可以填充到多个缓冲区中
ssize_t sockets::readv(int sockfd, const struct iovec *iov, int iovcnt)
{
  return ::readv(sockfd, iov, iovcnt);
}

ssize_t sockets::write(int sockfd, const void *buf, size_t count)
{
  return ::write(sockfd, buf, count);
}

void sockets::close(int sockfd)
{
  if (::close(sockfd) < 0)
  {
    LOG_SYSERR << "sockets::close";
  }
}

// 只关闭写的这一半
void sockets::shutdownWrite(int sockfd)
{
  if (::shutdown(sockfd, SHUT_WR) < 0)
  {
    LOG_SYSERR << "sockets::shutdownWrite";
  }
}

void sockets::toIpPort(char* buf, size_t size,
                       const struct sockaddr_in& addr)
{
  char host[INET_ADDRSTRLEN] = "INVALID";
  toIp(host, sizeof host, addr);
  uint16_t port = sockets::networkToHost16(addr.sin_port);
  snprintf(buf, size, "%s:%u", host, port);
}

void sockets::toIp(char* buf, size_t size,
                   const struct sockaddr_in& addr)
{
  assert(size >= INET_ADDRSTRLEN);
  ::inet_ntop(AF_INET, &addr.sin_addr, buf, static_cast<socklen_t>(size));
}

void sockets::fromIpPort(const char* ip, uint16_t port,
                           struct sockaddr_in* addr)
{
  addr->sin_family = AF_INET;
  addr->sin_port = hostToNetwork16(port);
  if (::inet_pton(AF_INET, ip, &addr->sin_addr) <= 0)
  {
    LOG_SYSERR << "sockets::fromIpPort";
  }
}

int sockets::getSocketError(int sockfd)
{
  int optval;
  socklen_t optlen = sizeof optval;

  if (::getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, &optlen) < 0)
  {
    return errno;
  }
  else
  {
    return optval;
  }
}

struct sockaddr_in sockets::getLocalAddr(int sockfd)
{
  struct sockaddr_in localaddr;
  bzero(&localaddr, sizeof localaddr);
  socklen_t addrlen = sizeof(localaddr);
  if (::getsockname(sockfd, sockaddr_cast(&localaddr), &addrlen) < 0)
  {
    LOG_SYSERR << "sockets::getLocalAddr";
  }
  return localaddr;
}

struct sockaddr_in sockets::getPeerAddr(int sockfd)
{
  struct sockaddr_in peeraddr;
  bzero(&peeraddr, sizeof peeraddr);
  socklen_t addrlen = sizeof(peeraddr);
  if (::getpeername(sockfd, sockaddr_cast(&peeraddr), &addrlen) < 0)
  {
    LOG_SYSERR << "sockets::getPeerAddr";
  }
  return peeraddr;
}

// 自连接是指(sourceIP, sourcePort) = (destIP, destPort)
// 自连接发生的原因:
// 客户端在发起connect的时候，没有bind(2)
// 客户端与服务器端在同一台机器，即sourceIP = destIP，
// 服务器尚未开启，即服务器还没有在destPort端口上处于监听
// 就有可能出现自连接，这样，服务器也无法启动了

bool sockets::isSelfConnect(int sockfd)
{
  struct sockaddr_in localaddr = getLocalAddr(sockfd);
  struct sockaddr_in peeraddr = getPeerAddr(sockfd);
  return localaddr.sin_port == peeraddr.sin_port
      && localaddr.sin_addr.s_addr == peeraddr.sin_addr.s_addr;
}

3.Socket.h

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)
//
// This is an internal header file, you should not include this.

#ifndef MUDUO_NET_SOCKET_H
#define MUDUO_NET_SOCKET_H

#include <boost/noncopyable.hpp>

namespace muduo
{
///
/// TCP networking.
///
namespace net
{

class InetAddress;

///
/// Wrapper of socket file descriptor.
///
/// It closes the sockfd when desctructs.
/// It's thread safe, all operations are delagated to OS.
class Socket : boost::noncopyable
{
 public:
  explicit Socket(int sockfd)
    : sockfd_(sockfd)
  { }

  // Socket(Socket&&) // move constructor in C++11
  ~Socket();

  int fd() const { return sockfd_; }

  /// abort if address in use
  void bindAddress(const InetAddress& localaddr);
  /// abort if address in use
  void listen();

  /// On success, returns a non-negative integer that is
  /// a descriptor for the accepted socket, which has been
  /// set to non-blocking and close-on-exec. *peeraddr is assigned.
  /// On error, -1 is returned, and *peeraddr is untouched.
  int accept(InetAddress* peeraddr);

  void shutdownWrite();

  ///
  /// Enable/disable TCP_NODELAY (disable/enable Nagle's algorithm).
  ///
  // Nagle算法可以一定程度上避免网络拥塞
  // TCP_NODELAY选项可以禁用Nagle算法
  // 禁用Nagle算法，可以避免连续发包出现延迟，这对于编写低延迟的网络服务很重要
  void setTcpNoDelay(bool on);

  ///
  /// Enable/disable SO_REUSEADDR
  ///
  void setReuseAddr(bool on);

  ///
  /// Enable/disable SO_KEEPALIVE
  ///
  // TCP keepalive是指定期探测连接是否存在，如果应用层有心跳的话，这个选项不是必需要设置的
  void setKeepAlive(bool on);

 private:
  const int sockfd_;
};

}
}
#endif  // MUDUO_NET_SOCKET_H

4.Socket.cc

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)

#include <muduo/net/Socket.h>

#include <muduo/net/InetAddress.h>
#include <muduo/net/SocketsOps.h>

#include <netinet/in.h>
#include <netinet/tcp.h>
#include <strings.h>  // bzero

using namespace muduo;
using namespace muduo::net;

Socket::~Socket()
{
  sockets::close(sockfd_);
}

void Socket::bindAddress(const InetAddress& addr)
{
  sockets::bindOrDie(sockfd_, addr.getSockAddrInet());
}

void Socket::listen()
{
  sockets::listenOrDie(sockfd_);
}

int Socket::accept(InetAddress* peeraddr)
{
  struct sockaddr_in addr;
  bzero(&addr, sizeof addr);
  int connfd = sockets::accept(sockfd_, &addr);
  if (connfd >= 0)
  {
    peeraddr->setSockAddrInet(addr);
  }
  return connfd;
}

void Socket::shutdownWrite()
{
  sockets::shutdownWrite(sockfd_);
}

void Socket::setTcpNoDelay(bool on)
{
  int optval = on ? 1 : 0;
  ::setsockopt(sockfd_, IPPROTO_TCP, TCP_NODELAY,
               &optval, sizeof optval);
  // FIXME CHECK
}

void Socket::setReuseAddr(bool on)
{
  int optval = on ? 1 : 0;
  ::setsockopt(sockfd_, SOL_SOCKET, SO_REUSEADDR,
               &optval, sizeof optval);
  // FIXME CHECK
}

void Socket::setKeepAlive(bool on)
{
  int optval = on ? 1 : 0;
  ::setsockopt(sockfd_, SOL_SOCKET, SO_KEEPALIVE,
               &optval, sizeof optval);
  // FIXME CHECK
}

5.InetAddress.h

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)
//
// This is a public header file, it must only include public header files.

#ifndef MUDUO_NET_INETADDRESS_H
#define MUDUO_NET_INETADDRESS_H

#include <muduo/base/copyable.h>
#include <muduo/base/StringPiece.h>

#include <netinet/in.h>

namespace muduo
{
namespace net
{

///
/// Wrapper of sockaddr_in.
///
/// This is an POD interface class.
class InetAddress : public muduo::copyable
{
 public:
  /// Constructs an endpoint with given port number.
  /// Mostly used in TcpServer listening.
  // 仅仅指定port，不指定ip，则ip为INADDR_ANY（即0.0.0.0）
  explicit InetAddress(uint16_t port);

  /// Constructs an endpoint with given ip and port.
  /// @c ip should be "1.2.3.4"
  InetAddress(const StringPiece& ip, uint16_t port);

  /// Constructs an endpoint with given struct @c sockaddr_in
  /// Mostly used when accepting new connections
  InetAddress(const struct sockaddr_in& addr)
    : addr_(addr)
  { }

  string toIp() const;
  string toIpPort() const;

  // __attribute__ ((deprecated)) 表示该函数是过时的，被淘汰的
  // 这样使用该函数，在编译的时候，会发出警告
  string toHostPort() const __attribute__ ((deprecated))
  { return toIpPort(); }

  // default copy/assignment are Okay

  const struct sockaddr_in& getSockAddrInet() const { return addr_; }
  void setSockAddrInet(const struct sockaddr_in& addr) { addr_ = addr; }

  uint32_t ipNetEndian() const { return addr_.sin_addr.s_addr; }
  uint16_t portNetEndian() const { return addr_.sin_port; }

 private:
  struct sockaddr_in addr_;
};

}
}

#endif  // MUDUO_NET_INETADDRESS_H

6.InetAddress.cc

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)

#include <muduo/net/InetAddress.h>

#include <muduo/net/Endian.h>
#include <muduo/net/SocketsOps.h>

#include <strings.h>  // bzero
#include <netinet/in.h>

#include <boost/static_assert.hpp>

// INADDR_ANY use (type)value casting.
#pragma GCC diagnostic ignored "-Wold-style-cast"
static const in_addr_t kInaddrAny = INADDR_ANY;
#pragma GCC diagnostic error "-Wold-style-cast"

//     /* Structure describing an Internet socket address.  */
//     struct sockaddr_in {
//         sa_family_t    sin_family; /* address family: AF_INET */
//         uint16_t       sin_port;   /* port in network byte order */
//         struct in_addr sin_addr;   /* internet address */
//     };

//     /* Internet address. */
//     typedef uint32_t in_addr_t;
//     struct in_addr {
//         in_addr_t       s_addr;     /* address in network byte order */
//     };

using namespace muduo;
using namespace muduo::net;

BOOST_STATIC_ASSERT(sizeof(InetAddress) == sizeof(struct sockaddr_in));

InetAddress::InetAddress(uint16_t port)
{
  bzero(&addr_, sizeof addr_);
  addr_.sin_family = AF_INET;
  addr_.sin_addr.s_addr = sockets::hostToNetwork32(kInaddrAny);
  addr_.sin_port = sockets::hostToNetwork16(port);
}

InetAddress::InetAddress(const StringPiece& ip, uint16_t port)
{
  bzero(&addr_, sizeof addr_);
  sockets::fromIpPort(ip.data(), port, &addr_);
}

string InetAddress::toIpPort() const
{
  char buf[32];
  sockets::toIpPort(buf, sizeof buf, addr_);
  return buf;
}

string InetAddress::toIp() const
{
  char buf[32];
  sockets::toIp(buf, sizeof buf, addr_);
  return buf;
}

7.InetAddress_unittest.cc

#include <muduo/net/InetAddress.h>

//#define BOOST_TEST_MODULE InetAddressTest
#define BOOST_TEST_MAIN
#define BOOST_TEST_DYN_LINK
#include <boost/test/unit_test.hpp>

using muduo::string;
using muduo::net::InetAddress;

BOOST_AUTO_TEST_CASE(testInetAddress)
{
  InetAddress addr1(1234);
  BOOST_CHECK_EQUAL(addr1.toIp(), string("0.0.0.0"));
  BOOST_CHECK_EQUAL(addr1.toIpPort(), string("0.0.0.0:1234"));

  InetAddress addr2("1.2.3.4", 8888);
  BOOST_CHECK_EQUAL(addr2.toIp(), string("1.2.3.4"));
  BOOST_CHECK_EQUAL(addr2.toIpPort(), string("1.2.3.4:8888"));

  InetAddress addr3("255.255.255.255", 65535);
  BOOST_CHECK_EQUAL(addr3.toIp(), string("255.255.255.255"));
  BOOST_CHECK_EQUAL(addr3.toIpPort(), string("255.255.255.255:65535"));
}

8.Endian.h

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)
//
// This is a public header file, it must only include public header files.

#ifndef MUDUO_NET_ENDIAN_H
#define MUDUO_NET_ENDIAN_H

#include <stdint.h>
#include <endian.h>

namespace muduo
{
namespace net
{
namespace sockets
{

// the inline assembler code makes type blur,
// so we disable warnings for a while.
#if __GNUC_MINOR__ >= 6
#pragma GCC diagnostic push
#endif
#pragma GCC diagnostic ignored "-Wconversion"
#pragma GCC diagnostic ignored "-Wold-style-cast"
inline uint64_t hostToNetwork64(uint64_t host64)
{
  return htobe64(host64);
}

inline uint32_t hostToNetwork32(uint32_t host32)
{
  return htobe32(host32);
}

inline uint16_t hostToNetwork16(uint16_t host16)
{
  return htobe16(host16);
}

inline uint64_t networkToHost64(uint64_t net64)
{
  return be64toh(net64);
}

inline uint32_t networkToHost32(uint32_t net32)
{
  return be32toh(net32);
}

inline uint16_t networkToHost16(uint16_t net16)
{
  return be16toh(net16);
}
#if __GNUC_MINOR__ >= 6
#pragma GCC diagnostic pop
#else
#pragma GCC diagnostic error "-Wconversion"
#pragma GCC diagnostic error "-Wold-style-cast"
#endif


}
}
}

#endif  // MUDUO_NET_ENDIAN_H

31muduo_net库源码分析（七）