简单RTP发送类c++实现

我之前编译了jrtplib 3.9.1，并且在项目中使用，结果发现在用这个库时，程序体积有增加了300多K，感觉实在是有点笨重，我无法就是用来发送rtp包而已。想想还是自己重新实现一个简单的类用用拉倒了，所以有了下面的代码。

头文件：

/*!
@brief 简单rtp库
@file easy_rtp.h
*/
#ifndef _EASY_RTP_H
#define _EASY_RTP_H

#include <string>

#include <stdint.h>

#ifdef _WIN32
#include <winsock2.h>
#else
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <errno.h>
#ifndef INVALID_SOCKET
#define INVALID_SOCKET  (SOCKET)(~0)
#endif
#ifndef SOCKET_ERROR
#define SOCKET_ERROR    (-1)
#endif
#ifndef closesocket
#define closesocket(x)  close(x)
#endif
typedef int SOCKET;
#endif

// 默认最大包大小(MTU 1500 - IP头 20 - UDP头 8)
#define DEFAULT_MAX_PACKET_SIZE 1472

/*!
@brief 简单rtp数据包装发送库
*/
class EasyRtp
{
public:
    /*!
    @brief 构造
    @param destIp 目标ip地址
    @param port 目标端口
    @param localport 本地帮定端口,默认端口采用随机值
    */
    EasyRtp(const std::string& destIp, uint16_t port, uint16_t localPort = 0, int16_t maxpacketsize = DEFAULT_MAX_PACKET_SIZE);
    /*!
    @brief 构造
    @param destIp 目标ip地址
    @param port 目标端口
    @param localport 本地帮定端口,默认端口采用随机值
    */
    EasyRtp(uint32_t destIp, uint16_t port, uint16_t localPort = 0, int16_t maxpacketsize = DEFAULT_MAX_PACKET_SIZE);
    ~EasyRtp();
public:
    /*!
    @brief 发送rtp包给目标
    @param buf 发送的缓冲
    @param len 发送的缓冲大小
    @param pt 负载类型
    @param mark 标记位
    @param timestampInc 时间戳增量
    @param 错误为-1
    */
    int32_t sendPacket(const char* buf, int32_t len, int8_t pt, bool mark, int32_t timestampInc);
private:
    /// 简单rtp头12字节,不含扩展头,csrc列表等信息
    typedef struct
    {
        uint8_t ver;                /// 版本号(2bit)
        bool p;                     /// 填充位,一直置0(1bit)
        bool x;                     /// 扩充头位,一直置0(1bit)
        uint8_t cc;                 /// csrc列表数量,一直置0(4bit)
        bool mark;                  /// 标记位(1bit)
        int8_t pt;                  /// 负载类型(7bit)
        uint16_t sn;                /// 序列号(16bit)
        uint32_t ts;                /// 时间戳(32bit)
        uint32_t ssrc;              /// 来源标示(32bit)
    }RtpHeader;

    // 最大包大小
    int16_t _maxPacketSize;
    // 发送的缓冲
    char* _sbuf;
    // 序列号
    uint16_t _sn;
    // 时间戳
    uint32_t _ts;
    // 源标示
    uint32_t _ssrc;
    // 句柄
    SOCKET _socket;
    // 目标地址
    struct sockaddr_in _destTo;
};

#endif  // _EASY_RTP_H

cpp源码：

#include <stdio.h>
#include <string.h>

#include <stdexcept>

#include "easy_rtp.h"
#include "byte_write.h"
#include "utils.h"

// 默认的rtp版本
#define RTP_VERSION         2
// rtp头大小
#define RTP_HEADER_SIZE     12

EasyRtp::EasyRtp( const std::string& destIp, uint16_t port, uint16_t localPort /*= 0*/, int16_t maxpacketsize /*= 1500*/ )
    :_maxPacketSize(maxpacketsize),
    _sbuf(NULL),
    _sn(Utils::createRandam32()),
    _ts(Utils::createRandam32()),
    _ssrc(Utils::createRandam32())
{
    if (maxpacketsize >= RTP_HEADER_SIZE)
        _sbuf = new char[maxpacketsize];
    else
        throw std::runtime_error("[EasyRtp] too small packet size, must more than 12 Byte");

    _socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
    if (_socket == INVALID_SOCKET)
        throw std::runtime_error("[EasyRtp] invalid socket");

    _destTo.sin_family = AF_INET;
    _destTo.sin_port = htons(port);
    _destTo.sin_addr.s_addr = inet_addr(destIp.c_str());

    if (localPort != 0)
    {
        struct sockaddr_in sockAddr;
        sockAddr.sin_family = AF_INET;
        sockAddr.sin_port = htons(localPort);
        sockAddr.sin_addr.s_addr = INADDR_ANY;

        if (bind(_socket, (const sockaddr*)&sockAddr, sizeof(sockAddr)) == SOCKET_ERROR)
        {
#ifndef NPRINT
#ifdef _WIN32
            printf("[EasyRtp] bind error: %d
", WSAGetLastError());
#else
            printf("[EasyRtp] bind error: %d
", errno);
#endif
#endif
            closesocket(_socket);
            throw std::runtime_error("[EasyRtp] bind error");
        }
    }
}

EasyRtp::EasyRtp( uint32_t destIp, uint16_t port, uint16_t localPort /*= 0*/, int16_t maxpacketsize /*= DEFAULT_MAX_PACKET_SIZE*/ )
    :_maxPacketSize(maxpacketsize),
    _sbuf(NULL),
    _sn(Utils::createRandam32()),
    _ts(Utils::createRandam32()),
    _ssrc(Utils::createRandam32())
{
    if (maxpacketsize >= RTP_HEADER_SIZE)
        _sbuf = new char[maxpacketsize];
    else
        throw std::runtime_error("[EasyRtp] too small packet size, must more than 12 Byte");

    _socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
    if (_socket == INVALID_SOCKET)
        throw std::runtime_error("[EasyRtp] invalid socket");

    _destTo.sin_family = AF_INET;
    _destTo.sin_port = htons(port);
    _destTo.sin_addr.s_addr = htonl(destIp);

    if (localPort != 0)
    {
        struct sockaddr_in sockAddr;
        sockAddr.sin_family = AF_INET;
        sockAddr.sin_port = htons(localPort);
        sockAddr.sin_addr.s_addr = INADDR_ANY;

        if (bind(_socket, (const sockaddr*)&sockAddr, sizeof(sockAddr)) == SOCKET_ERROR)
        {
#ifndef NPRINT
#ifdef _WIN32
            printf("[EasyRtp] bind error: %d
", WSAGetLastError());
#else
            printf("[EasyRtp] bind error: %d
", errno);
#endif
#endif
            closesocket(_socket);
            throw std::runtime_error("[EasyRtp] bind error");
        }
    }
}

EasyRtp::~EasyRtp()
{
    if (_socket != INVALID_SOCKET)
        closesocket(_socket);
    if (_sbuf != NULL)
        delete [] _sbuf;
}

int32_t EasyRtp::sendPacket( const char* buf, int32_t len, int8_t pt, bool mark, int32_t timestampInc )
{
    if ((len + RTP_HEADER_SIZE) > _maxPacketSize)
        return -1;

    ++_sn;
    _ts += timestampInc;

    // 只设置版本号,其它的全是默认0
    _sbuf[0] = 0;
    _sbuf[0] |= RTP_VERSION << 6;
    _sbuf[1] = 0;
    _sbuf[1] |= mark << 7;
    _sbuf[1] |= pt;
    write_be_w(_sbuf + 2, _sn);
    write_be_dw(_sbuf + 4, _ts);
    write_be_dw(_sbuf + 8, _ssrc);
    // 保存数据
    memcpy(_sbuf + RTP_HEADER_SIZE, buf, len);
    int32_t ret = sendto(_socket, (const char*)_sbuf, len + RTP_HEADER_SIZE, 0, (const sockaddr*)&_destTo, sizeof(_destTo));
#ifndef NPRINT
    if (ret < 0)
    {
#ifdef _WIN32
        printf("[EasyRtp] sendto error: %d
", WSAGetLastError());
#else
        printf("[EasyRtp] sendto error: %d
", errno);
#endif
    }
#endif
    return ret;
}

注：

stdint.h是新c++标准中的头文件，定义了int32_t int8_t等typedef 类型。