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webRTC使用记录1

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本小节是 webrtc 前置内容，主要介绍 tcp 跟 udp 的 server 及 client 端实现代码。

tips：c 语言实现，demo 级别，仅供一对一通讯。

参考自慕课网 百万级高并发WebRTC流媒体服务器设计与开发

udp 是无连接的，绑定了端口后直接进行收发处理，不需要监听。

TCP连接相关结构体

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struct sockaddr_in{
	sa_family_t     sin_family; //什么协议，如 ipv4 or ipv6
	uint16_t        sin_port;   // port addr
	struct in_addr  sin_addr;   // ip addr
	char            sin_zero[8] // 默认 0
} // 用于服务端设置ip 和 port
struct in_addr{
  in_addr_t       s_addr; // ip addr，一般整型存储
}

struct sockaddr{
	sa_family_t     sin_family; //什么协议，如 ipv4 or ipv6
	char            sin_zero[8] // 默认 0
}

Tcp_server 端的c实现demo

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// tcp_server.c
// 1. 创建 socket(socket_fd; 2. 配置 sin 相关; 3. bind; 4. listen;
// 5. accept & 生成 accept_fd; 5.5 loop 接收请求;
// 6. 结束时关闭 accept_fd; 7. 最终结束时关闭 socket_fd
//
//应该传入local_addr、remote_addr

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define PORT 8444
#define MESSAGE_SIZE 1024

int main(){
  int ret = -1;
  int socket_fd = -1;
  int accept_fd = -1;
  int curpos = 0;
  int backlog = 10;
  int flag = 1;
  char in_buf[MESSAGE_SIZE] = {0,};
  struct sockaddr_in local_addr, remote_addr;

  //create a tcp socket
  socket_fd = socket(AF_INET, SOCK_STREAM, 0);
  if ( socket_fd == -1 ){
    perror("create socket error");
    exit(1);
  }

  //set option of socket
  ret = setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(flag));
  if ( ret == -1 ){
    perror("setsockopt error");
  }

  //set local address
  local_addr.sin_family = AF_INET;
  local_addr.sin_port = htons(PORT);
  local_addr.sin_addr.s_addr = INADDR_ANY;
  bzero(&(local_addr.sin_zero), 8);

  //bind socket
  ret = bind(socket_fd, (struct sockaddr *)&local_addr, sizeof(struct sockaddr_in));
  if(ret == -1 ) {
    perror("bind error");
    exit(1);
  }
  ret = listen(socket_fd, backlog);
  if ( ret == -1 ){
    perror("listen error");
    exit(1);
  }

  //loop
  for(;;){
    int addr_len = sizeof( struct sockaddr_in );
    //accept an new connection
    accept_fd = accept( socket_fd, (struct sockaddr *)&remote_addr, &addr_len );
    for(;;){
      memset(in_buf, 0, MESSAGE_SIZE);
      //receive network data and print it
      ret = recv( accept_fd ,(void*)in_buf ,MESSAGE_SIZE ,0 );
      if(ret == 0 ){
        break; 
      } 
      printf( "receive message:%s\n", in_buf );
      send(accept_fd, (void*)in_buf, MESSAGE_SIZE, 0); 
    }
    printf("close client connection...\n");
    close(accept_fd);
  }
  printf("quit server...\n");
  close(socket_fd);
  return 0;
}

Tcp_client 端的 c 实现demo

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// tcp_client.c
// 1. 创建 socket; 2. connect;
// 3. loop send & receive; 4. quit & close
//
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <netdb.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define SERVER_PORT 8111
#define MESSAGE_LENGTH 1024

int main(){
  int ret = -1;
  int socket_fd;
  //server addr
  struct sockaddr_in serverAddr;
  char sendbuf[MESSAGE_LENGTH];
  char recvbuf[MESSAGE_LENGTH];
  int data_len;

  if((socket_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
    perror("socket");
    return 1;
  }
  serverAddr.sin_family = AF_INET;
  serverAddr.sin_port = htons(SERVER_PORT);
  //inet_addr()函数，将点分十进制IP转换成网络字节序IP
  serverAddr.sin_addr.s_addr = inet_addr("39.105.185.198");
  //serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
  
  // connect
  if(connect(socket_fd, (struct sockaddr *)&serverAddr, sizeof(serverAddr)) < 0){
    perror("connect");
    return 1;
  }
  printf("success to connect server...\n");
  // loop send and receive data
  while(1){
    memset(sendbuf, 0, MESSAGE_LENGTH);
    printf("<<<<send message:");
    gets(sendbuf);
    //printf("\n");
    ret = send(socket_fd, sendbuf, strlen(sendbuf), 0);
    if(ret <= 0 ){
      printf("the connection is disconnection!\n"); 
      break;
    }
    if(strcmp(sendbuf, "quit") == 0){
      // 收到 quit 关键词，退出
      break;
    }
    printf(">>> echo message:");
    recvbuf[0] = '\0';
    data_len = recv(socket_fd, recvbuf, MESSAGE_LENGTH, 0);
    recvbuf[data_len] = '\0';
    printf("%s\n", recvbuf);
  }
  close(socket_fd);
  return 0;
}

UDP_server 端的 c 实现demo

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// upd_server.c
#include <sys/types.h>
#include <sys/socket.h>
#include <pthread.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <arpa/inet.h>

int main(int argc, char * *argv){
  struct sockaddr_in addr;
  addr.sin_family     = AF_INET;
  addr.sin_port       = htons(9876);
  addr.sin_addr.s_addr = htonl(INADDR_ANY);
  char buff_recv[512] = {0};
  char buff_send[512] = "world";
  struct sockaddr_in clientAddr;
  int n;
  int len = sizeof(clientAddr);
  int sock;   
  printf("Welcome! This is a UDP server.\n");
  
  if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) < 0){
      printf("socket error.\n");
      exit(1);
  }
  if (bind(sock, (struct sockaddr *) &addr, sizeof(addr)) < 0){
    printf("bind error.\n");
    exit(1);
  }
  while (1){
    n = recvfrom(sock, buff_recv, 511, 0, (struct sockaddr *) &clientAddr, &len);
    if (n > 0){
      buff_recv[n] = 0;
      printf("recv data from client:%s %u says: %s\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port), buff_recv);
      n = sendto(sock, buff_send, n, 0, (struct sockaddr *) &clientAddr, sizeof(clientAddr));
      if (n < 0){
        printf("sendto error.\n");
        break;
      }else {
        printf("recv error.\n");
        break;
      }
    }
    return 0;
  }

Udp_client 端的 c 实现demo

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// udp_client.c

#include <sys/types.h>
#include <sys/socket.h>
#include <pthread.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

int main(int argc, char * *argv){   
    struct sockaddr_in addr;
    int sock;
    addr.sin_family     = AF_INET;
    addr.sin_port       = htons(9876);
    addr.sin_addr.s_addr = inet_addr("111.231.68.13");
    char buff_send[512] = "Hello";
    char buff_recv[512] = {0};
    int len = sizeof(addr);
    int n = 0;
    printf("This is a UDP client\n");
    if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) < 0){
      printf("socket error.\n");
      exit(1);
    }
    if (addr.sin_addr.s_addr == INADDR_NONE){
      printf("Incorrect ip address!");
      close(sock);
      exit(1);
    }
    n = sendto(sock, buff_send, strlen(buff_send), 0, (struct sockaddr *) &addr, sizeof(addr));
    if (n < 0){
      printf("sendto error.\n");
      close(sock);
    }
    n = recvfrom(sock, buff_recv, 512, 0, (struct sockaddr *) &addr, &len);
    if (n > 0){
        buff_recv[n] = 0;
        printf("received from sever:");
        puts(buff_recv);
    }
    else if (n == 0)
        printf("server closed.\n");
    else if (n == -1)
        printf("recvfrom error.\n");
    close(sock);
    return 0;
}

现在问题来了：

使用 while(1)或者其他死循环接收信息的方式，在多 client 的场景下，仅第一个连接上的 client 可以跟 server 通讯，其他 client 虽然也能连接上，但无法传输数据。

解决办法通常有：

  1. fork

  2. select

  3. epoll

  4. IO事件库

    详见下一节内容。

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