建立sctp編譯環境

直接透過apt取得sctp的套件

$ sudo apt-get install libsctp-dev lksctp-tools
下面有一個範例程式：
server.c

//==============================include header file============================
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/sctp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
//=============================================================================

//==============================define variable================================
#define BUFFERSIZE 8192
#define SERV_PORT 9877
#define LISTENQ 1024
//=============================================================================

int main(int argc,char **argv)
{
  int echo_to_all = 0;

  int ret_value;
  int sock_fd;
  int msg_flags;  // 記錄要傳送訊息時的相關設定
  char readbuf[BUFFERSIZE];
  struct sockaddr_in servaddr,cliaddr;
  struct sctp_sndrcvinfo sri;     // 記錄send, recv, association的相關資訊
  struct sctp_event_subscribe evnts;
  int stream_increment = 1;
  socklen_t len;
  size_t rd_sz;   // size_t指的就是unsigned long:rd_sz表示recv,send-size

  if (argc == 2) {
    // 把字串轉換成數字
    stream_increment = atoi(argv[1]);
  }

  // 建立socket的型態為SCTP的one-to-many的型態
  sock_fd = socket(AF_INET,SOCK_SEQPACKET,IPPROTO_SCTP);
  if (sock_fd == -1) {
    printf("socket error\n");
    exit(-1);
  }
  // 初始化server address的設定
  memset(&servaddr,0,sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  servaddr.sin_port = htons(SERV_PORT);

  // 把socket與所建立的address綁在一起
  ret_value = bind(sock_fd,(struct sockaddr *) &servaddr,sizeof(servaddr));
  if (ret_value == -1) {
    printf("bind error\n");
    exit(-1);
  }

  // Set up for notifications of internet
  bzero(&evnts,sizeof(evnts));
  evnts.sctp_data_io_event = 1;   // 使得sctp_sndrcvinfo可以伴隨資料傳送過來
  ret_value = setsockopt(sock_fd,IPPROTO_SCTP,SCTP_EVENTS,&evnts,sizeof(evnts));
  if (ret_value == -1) {
    printf("setsockopt error\n");
    exit(-1);
  }

  // 設定等待多少個client端連線
  ret_value = listen(sock_fd,LISTENQ);
  if (ret_value == -1) {
    printf("listen error\n");
    exit(-1);
  }

  printf("start wait...\n");
  for (;;) {
    len = sizeof(struct sockaddr_in);
    // 等待client端連線
    rd_sz = sctp_recvmsg(sock_fd,readbuf,sizeof(readbuf),(struct sockaddr *) &cliaddr,&len,&sri,&msg_flags);
    if (stream_increment) {
      sri.sinfo_stream++;
      if (sri.sinfo_stream >= 100) {
        sri.sinfo_stream = 0;
      }
    }
    // 把接收到的資料回送給client
    ret_value = sctp_sendmsg(sock_fd,readbuf,rd_sz,(struct sockaddr *) &cliaddr,len,sri.sinfo_ppid,sri.sinfo_flags,sri.sinfo_stream,0,0);
    if (ret_value == -1) {
      printf("sctp_sendmsg error\n");
      exit(-1);
    }
  }
  return 0;
}

client.c

//==============================include header file============================
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/sctp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
//=============================================================================

//==============================define variable================================
#define BUFFERSIZE 8192
#define SERV_PORT 9877
#define LISTENQ 1024
#define MAXLINE 4096
#define SCTP_MAXLINE 800
#define SERV_MAX_SCTP_STRM 10
//=============================================================================

//==============================define function================================
void sctpstr_cli(FILE *fp,int sock_fd,struct sockaddr *to,socklen_t tolen);
void sctpstr_cli_echoall(FILE *fp,int sock_fd,struct sockaddr *to,socklen_t tolen);
//=============================================================================

//==============================main function==================================
int main(int argc,char **argv)
{
  int sock_fd;    // client所建立的socket
  struct sockaddr_in servaddr;    // 記錄server的sockaddr_in的相關資訊
  struct sctp_event_subscribe evnts;      // 設定要觀查的事件
  int echo_to_all = 0;      // 決定server是否有多個
  int ret_value = 0;
    
  // 沒有設定server的ip
  if (argc < 2) {
    printf("Missing host argument - use '%s host [echo]'\n",argv[0]);
    exit(-1);
  }
  // 設定多個server的ip
  if (argc > 2) {
    printf("Echoing messages to all streams\n");
    echo_to_all = 1;
  }

  // init setting
  sock_fd = socket(AF_INET,SOCK_SEQPACKET,IPPROTO_SCTP);  // 設定為sctp為one-to-many的型態
  bzero(&servaddr,sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr = htonl(INADDR_ANY);   // 感覺這一行應該是多餘的
  servaddr.sin_port = htons(SERV_PORT);
  ret_value = inet_pton(AF_INET,argv[1],&servaddr.sin_addr);      // 把字串轉換成網路位元組序二進位值,當回傳為1時,表轉換
成功
  if (ret_value != 1) {
    printf("translate server ip address error!!\n");
    exit(-1);
  }

  // 設定要觀察的事件,所有都清除,只設定io event
  memset(&evnts,0,sizeof(evnts));
  evnts.sctp_data_io_event = 1;   // 監控sctp的data的io事件:1是打開的意思
  ret_value = setsockopt(sock_fd,IPPROTO_SCTP,SCTP_EVENTS,&evnts,sizeof(evnts));
  if (ret_value == -1) {
    printf("setsockopt error\n");
    exit(-1);
  }
  if (echo_to_all == 0) {
    // 此client只傳給一個server
    sctpstr_cli(stdin,sock_fd,(struct sockaddr *) &servaddr,sizeof(servaddr));
  }
  else {
    // 要設定傳給許多個server
    sctpstr_cli_echoall(stdin,sock_fd,(struct sockaddr *) &servaddr,sizeof(servaddr));
  }
  close(sock_fd);
  return 0;
}
//=============================================================================

//==============================function implemen==============================
void sctpstr_cli(FILE *fp,int sock_fd,struct sockaddr *to,socklen_t tolen)
{
  struct sockaddr_in peeraddr;    // client的相關位址資料
  struct sctp_sndrcvinfo sri;     // send and recv端的資料
  char sendline[MAXLINE],recvline[MAXLINE];
  socklen_t len;
  int out_sz,rd_sz;
  int msg_flags;
  int ret_value=0;

  bzero(&sri,sizeof(sri));
  // block住,等待client端輸入
  while (fgets(sendline,MAXLINE,fp) != NULL) {
    if (sendline[0] != '[') {
      printf("Error, line must be of the form '[streamnum]text'\n");
      continue;
    }
    // string to long integer,表示sendline這一個字串是base在10進位去轉換
    // 透過設定的stream number來傳送資料
    sri.sinfo_stream = strtol(&sendline[1],NULL,0);
    out_sz = strlen(sendline);      // 輸入字串的長度,用來記錄等一下要傳送幾個字元
    ret_value = sctp_sendmsg(sock_fd,sendline,out_sz,to,tolen,0,0,sri.sinfo_stream,0,0);
    if (ret_value == -1) {
      printf("sctp_sendmsg error\n");
      exit(-1);
    }

    len = sizeof(peeraddr);
    rd_sz = sctp_recvmsg(sock_fd,recvline,sizeof(recvline),(struct sockaddr *) &peeraddr,&len,&sri,&msg_flags);
    printf("From str:%d seq:%d (assoc:0x%x):",sri.sinfo_stream,sri.sinfo_ssn,(u_int) sri.sinfo_assoc_id);
    printf("%.*s",rd_sz,recvline);
  }
}

void sctpstr_cli_echoall(FILE *fp,int sock_fd,struct sockaddr *to,socklen_t tolen)
{
  struct sockaddr_in peeraddr;
  struct sctp_sndrcvinfo sri;
  char sendline[SCTP_MAXLINE], recvline[SCTP_MAXLINE];
  socklen_t len;
  int rd_sz,i,strsz;
  int msg_flags;
  int ret_value=0;

  // the client initializes the sri structure used to set up the stream it will be sending and receiving from
  bzero(sendline,sizeof(sendline));
  bzero(&sri,sizeof(sri));
  while(fgets(sendline,SCTP_MAXLINE-9,fp) != NULL) {
    strsz = strlen(sendline);
    // delete the newline character that is at the end of the buffer
    if (sendline[strsz-1] == '\n') {
      sendline[strsz-1]='\0';
      strsz--;
    }
    // 傳送SERV_MAX_SCTP_STRM筆資料給server
    for (i=0;i<SERV_MAX_SCTP_STRM;i++) {
      snprintf(sendline+strsz,sizeof(sendline)-strsz,".msg.%d",i);
      ret_value = sctp_sendmsg(sock_fd,sendline,sizeof(sendline),to,tolen,0,0,i,0,0);
      if (ret_value == -1) {
        printf("sctp_sendmsg error\n");
        exit(-1);
      }
    }
    // 由server接收SERV_MAX_SCTP_STRM筆資料
    for (i=0;i<SERV_MAX_SCTP_STRM;i++) {
      len = sizeof(peeraddr);
      rd_sz = sctp_recvmsg(sock_fd,recvline,sizeof(recvline),(struct sockaddr *) &peeraddr,&len,&sri,&msg_flags);
      printf("From str:%d seq:%d (assoc:0x%x):",sri.sinfo_stream,sri.sinfo_ssn,(u_int) sri.sinfo_assoc_id);
      printf("%.*s\n",rd_sz,recvline);
    }
  }
}

編譯：
$ gcc server.c -o server -lsctp
$ gcc client.c -o client -lsctp
$ ./server &
$ ./client 127.0.0.1
> [1]Hello World!!

參考資料：
網絡編程基礎--學習筆記
UNIX Network Programming
sctp_exporter.cc
SCTP Ancillary Data Structures
Stream Control Transmission Protocol