LINUX编程实战指发送UDP消息

最近调试媒体服务器，发现被叫的媒体流总是抖动的厉害，不清楚是网络原因还是媒体服务器的代码问题。

为了方便排查问题，我编写了一个UDP发送的小工具。根据传入目的地的IP、PORT和发送的时长。该工具就可以按照20ms的间隔进行重复发送RTP流。

编程思路：

首先初始化本端udp的socket套接字：

memset(buf,1,sizeof(buf));
	char * desip = argv[1];
	int destport = atoi(argv[2]);
	int sec = atoi(argv[3]);
	int count = sec * 1000 / 20;
	int fd=-1;
  fd=socket(AF_INET,SOCK_DGRAM,0);
  fcntl(fd,F_SETFL,O_NDELAY);
  int reuse_addr_flag=1;
  int success=setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,(char *)&reuse_addr_flag,sizeof(reuse_addr_flag));
  if(success<0)
  {
      perror("udp setsockopt(SO_REUSEADDR): ");
      close(fd);
      return 0;
  }
   int sendBufSize,sendBufLength;
   sendBufSize=4*1024*1024;
   sendBufLength=sizeof sendBufSize;

   if(setsockopt(fd,SOL_SOCKET,SO_SNDBUF,(char*)&sendBufSize,sendBufLength)<0)
   {
      perror("udp setsockopt(SO_SNDBUF): ");
      return 0;
   }
   if(setsockopt(fd,SOL_SOCKET,SO_RCVBUF,(char*)&sendBufSize,sendBufLength)<0)
   {
      perror("udp setsockopt(SO_RCVBUF): ");
      return 0;
   }
   struct sockaddr_in localaddr;
   in_addr_t net_addr=inet_addr("0.0.0.0");
   //ntohl(l_ipv4.ip_dw)
	 memset(&localaddr,0,sizeof(struct sockaddr_in));
	 localaddr.sin_family = AF_INET;
	 localaddr.sin_port = 30008;
	 memcpy((struct sockaddr*)&localaddr.sin_addr,(void *)(&net_addr),sizeof(net_addr));
	 if (bind(fd,(struct sockaddr *)&localaddr,sizeof(struct sockaddr_in)) != 0)
	 {
		return 0;
	 }

根据目的端的IP、PORT设置套接字：

int success;
   struct sockaddr *pDestAddr = NULL;
   struct sockaddr_in destAddr;
   int len;
   memset(&destAddr,0,sizeof(struct sockaddr_in));
   in_addr_t net_addr=inet_addr(host);
   destAddr.sin_family = AF_INET;            
   destAddr.sin_port = htons(port);
   memcpy((struct sockaddr*)&destAddr.sin_addr,(void *)(&net_addr),sizeof(net_addr));
   pDestAddr = (struct sockaddr*)&destAddr;
   len = sizeof(destAddr);

最后调用sendto函数，发送UDP数据

success = sendto(fd,buffer,length,0, pDestAddr, len);
   if(success<0)
   {
      char *buf = new char[length + 128];
      sprintf(buf, "sendto(%d, %s, %d, %s, %d):", fd, buffer, length, host, port);
      perror(buf);
      delete []buf;
   }

完整的代码如下：

#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <strings.h> 
#include <signal.h>
#include <unistd.h>

#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <time.h>
#include <sys/time.h>
#include <unistd.h>

void sendUDPMsg(int fd,char* host,unsigned short port,char* buffer,int length);
int main(int argc,char* argv[])
{
	char buf[640]={1};
	memset(buf,1,sizeof(buf));
	char * desip = argv[1];
	int destport = atoi(argv[2]);
	int sec = atoi(argv[3]);
	int count = sec * 1000 / 20;
	int fd=-1;
  fd=socket(AF_INET,SOCK_DGRAM,0);
  fcntl(fd,F_SETFL,O_NDELAY);
  int reuse_addr_flag=1;
  int success=setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,(char *)&reuse_addr_flag,sizeof(reuse_addr_flag));
  if(success<0)
  {
      perror("udp setsockopt(SO_REUSEADDR): ");
      close(fd);
      return 0;
  }
   int sendBufSize,sendBufLength;
   sendBufSize=4*1024*1024;
   sendBufLength=sizeof sendBufSize;

   if(setsockopt(fd,SOL_SOCKET,SO_SNDBUF,(char*)&sendBufSize,sendBufLength)<0)
   {
      perror("udp setsockopt(SO_SNDBUF): ");
      return 0;
   }
   if(setsockopt(fd,SOL_SOCKET,SO_RCVBUF,(char*)&sendBufSize,sendBufLength)<0)
   {
      perror("udp setsockopt(SO_RCVBUF): ");
      return 0;
   }
   struct sockaddr_in localaddr;
   in_addr_t net_addr=inet_addr("0.0.0.0");
   //ntohl(l_ipv4.ip_dw)
	 memset(&localaddr,0,sizeof(struct sockaddr_in));
	 localaddr.sin_family = AF_INET;
	 localaddr.sin_port = 30008;
	 memcpy((struct sockaddr*)&localaddr.sin_addr,(void *)(&net_addr),sizeof(net_addr));
	 if (bind(fd,(struct sockaddr *)&localaddr,sizeof(struct sockaddr_in)) != 0)
	 {
		return 0;
	 }
	 
	 int i =0;
	 for(i=0;i<count;i++)
	 {
	 	 sendUDPMsg(fd,desip,destport,buf,sizeof(buf));
	 	 usleep(1000 * 20);
	 }
	 return 1;
}

void sendUDPMsg(int fd,char* host,unsigned short port,char* buffer,int length)
{   
   int success;
   struct sockaddr *pDestAddr = NULL;
   struct sockaddr_in destAddr;
   int len;
   memset(&destAddr,0,sizeof(struct sockaddr_in));
   in_addr_t net_addr=inet_addr(host);
   destAddr.sin_family = AF_INET;            
   destAddr.sin_port = htons(port);
   memcpy((struct sockaddr*)&destAddr.sin_addr,(void *)(&net_addr),sizeof(net_addr));
   pDestAddr = (struct sockaddr*)&destAddr;
   len = sizeof(destAddr);
   success = sendto(fd,buffer,length,0, pDestAddr, len);
   if(success<0)
   {
      char *buf = new char[length + 128];
      sprintf(buf, "sendto(%d, %s, %d, %s, %d):", fd, buffer, length, host, port);
      perror(buf);
      delete []buf;
   }
}

代码编译方法如下：

g++ -g testrtpudp.c -o testrtp

使用方法如下：

./testrtp 192.168.2.77 3950 1