recv一次最大可以收多少字符

recv一次最大可以收多少字符

65535ip包的最大值

szBuf的长度类型是UINT，结合应用考虑，等于是没有长度上的限制。 （通常根据需要和硬件资源，设定在几K以内） recv函数在未收到指定字节数时阻塞，直到收够指定字节数或超时或对方关闭SOCKET； 如果指定接收数目小于传过来的数目，则剩余字节在系统的SOCKET缓冲区中（当系统缓冲区满时，对方发送线程自动阻塞，停止发送），可以再次调用recv读取，（如果SOCKET关闭，则未接收数据丢失）。

windows: 1.简单服务器 //#include //#pragma comment(lib,"ws2_32.lib") wsadata wsd; static uint port=%%1; uint listen(lpvoid pparam) { socket sserver,sclient; char buf[1024]; int retval; if(wsastartup(makeword(2,2),&wsd)!=0) { return -1;//失败 } sserver=socket(af_inet,sock_stream,ipproto_tcp); if(invalid_socket==sserver) { wsacleanup(); return -1;//创建套接字失败 } sockaddr_in addrserv; addrserv.sin_family=af_inet; addrserv.sin_port=htons((short)pparam); addrserv.sin_addr.s_addr=inaddr_any; retval=bind(sserver,(lpsockaddr)&addrserv,sizeof(sockaddr_in)); if(socket_error==retval) { closesocket(sserver); wsacleanup(); return -1;//绑定套接字失败 } retval=listen(sserver,1); if(socket_error==retval) { closesocket(sserver); wsacleanup(); return -1;//开始监听失败 } sockaddr_in addrclient; int addrclientlen=sizeof(addrclient); sclient=accept(sserver,(sockaddr far*)&addrclient,&addrclientlen); if(invalid_socket==sclient) { closesocket(sserver); wsacleanup(); return -1;//开始接受客户端连接失败 } zeromemory(buf,sizeof(buf)); retval=recv(sclient,buf,sizeof(buf),0); if(socket_error==retval) { closesocket(sserver); closesocket(sclient); wsacleanup(); return -1;//接收数据失败 } cstring %%2(buf); closesocket(sserver); closesocket(sclient); wsacleanup(); return 0; } cwinthread *pthread=afxbeginthread(listen,&port); 2.简单客户端 //#include //#pragma comment(lib,"ws2_32.lib") wsadata wsd; socket shost; sockaddr_in servaddr; char buf[1024]; int retval; if(wsastartup(makeword(2,2),&wsd)!=0) { return -1;//失败 } shost=socket(af_inet,sock_stream,ipproto_tcp); if(invalid_socket==shost) { wsacleanup(); return -1;//创建套接字失败 } servaddr.sin_family=af_inet; servaddr.sin_addr.s_addr=inet_addr(%%3); servaddr.sin_port=htons((short)%%2); int nservaddlen=sizeof(servaddr); retval=connect(shost,(lpsockaddr)&servaddr,sizeof(servaddr)); if(socket_error==retval) { closesocket(shost); wsacleanup(); return -1;//连接服务器失败 } zeromemory(buf,sizeof(buf)); strcpy(buf,%%3); retval=send(shost,buf,sizeof(buf),0); if(socket_error==retval) { closesocket(shost); wsacleanup(); return -1;//向服务器发送数据失败 } closesocket(shost); wsacleanup(); 3.获得本机ip //#include //#pragma comment(lib,"ws2_32.lib") wsadata wsd; if(wsastartup(makeword(2,2),&wsd)!=0) { return -1;//失败 } char szhostname[100],szhostaddress[200]; if(gethostname(szhostname,sizeof(szhostname))!=socket_error) { hostent *phostent=gethostbyname(szhostname); if(phostent!=null){ sprintf(szhostaddress,"%d.%d.%d.%d", ( phostent->h_addr_list[0][0]&0x00ff ), ( phostent->h_addr_list[0][1]&0x00ff ), ( phostent->h_addr_list[0][2]&0x00ff ), ( phostent->h_addr_list[0][3]&0x00ff )); } } else return; cstring %%1(szhostaddress); unix: 1.简单客户端 if((sockfd=socket(af_inet,sock_stream,0))==-1) { fprintf(stderr,"socket error:%s\a\n",strerror(errno)); exit(1); } bzero(&server_addr,sizeof(server_addr)); server_addr.sin_family=af_inet; server_addr.sin_port=htons(portnumber); server_addr.sin_addr=*((struct in_addr *)host-?h_addr); if(connect(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1) { fprintf(stderr,"connect error:%s\a\n",strerror(errno)); exit(1); } if((nbytes=read(sockfd,buffer,1024))==-1) { fprintf(stderr,"read error:%s\n",strerror(errno)); exit(1); } buffer[nbytes]=’\0′; printf("i have received:%s\n",buffer); close(sockfd); exit(0); } */ int sock_connect(char *domain,int port) { int white_sock; struct hostent * site; struct sockaddr_in me; site = gethostbyname(domain); if (site==null) return -2; white_sock = socket(af_inet,sock_stream,0); if (white_sock?0) return -1; memset(&me,0,sizeof(struct sockaddr_in)); memcpy(&me.sin_addr,site-?h_addr_list[0],site-?h_length); me.sin_family = af_inet; me.sin_port = htons(port); return (connect(white_sock,(struct sockaddr *)&me,sizeof(struct sockaddr))?0) ? -1 : white_sock; } 2.简单服务器端 #include #include #include #include #include #include #include #include int main(int argc, char *argv[]) { int sockfd,new_fd; struct sockaddr_in server_addr; struct sockaddr_in client_addr; int sin_size,portnumber; char hello[]="hello! are you fine?\n"; if(argc!=2) { fprintf(stderr,"usage:%s portnumber\a\n",argv[0]); exit(1); } if((portnumber=atoi(argv[1]))?0) { fprintf(stderr,"usage:%s portnumber\a\n",argv[0]); exit(1); } if((sockfd=socket(af_inet,sock_stream,0))==-1) { fprintf(stderr,"socket error:%s\n\a",strerror(errno)); exit(1); } bzero(&server_addr,sizeof(struct sockaddr_in)); server_addr.sin_family=af_inet; server_addr.sin_addr.s_addr=htonl(inaddr_any); server_addr.sin_port=htons(portnumber); if(bind(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1) { fprintf(stderr,"bind error:%s\n\a",strerror(errno)); exit(1); } if(listen(sockfd,5)==-1) { fprintf(stderr,"listen error:%s\n\a",strerror(errno)); exit(1); } while(1) { sin_size=sizeof(struct sockaddr_in); if((new_fd=accept(sockfd,(struct sockaddr *)(&client_addr),&sin_size))==-1) { fprintf(stderr,"accept error:%s\n\a",strerror(errno)); exit(1); } fprintf(stderr,"server get connection from %s\n", inet_ntoa(client_addr.sin_addr)); if(write(new_fd,hello,strlen(hello))==-1) { fprintf(stderr,"write error:%s\n",strerror(errno)); exit(1); } close(new_fd); } close(sockfd); exit(0); } 客户端程序 */ int daemonsocket; struct sockaddr_in daemonaddr; int bindsocket(void) { daemonsocket = socket(af_inet,sock_stream,0); if (daemonsocket==-1) return 0; daemonaddr.sin_family = af_inet; daemonaddr.sin_port = htons(daemon_port); if (bind(daemonsocket,&daemonaddr,sizeof(daemonaddr))?0) { printf("can not bind!\n"); return 0; } if (listen(daemonsocket,1024)!=0) { printf("can not listen!\n"); return 0; } return 1; } //要查看是否有连线进来，可用以下方式: int incoming_call(void) { fd_set sock; struct timeval tv; int t; fd_zero(&sock); fd_set(daemonsocket,&sock); tv.tv_sec = 60; tv.tv_usec = 0; t = select(daemonsocket + 1,&sock,null,null,&tv); if (t?=0||!fd_isset(daemonsocket,&sock)) return 0; printf("incoming…\n"); return 1; } //connect client //当我们确认有人进来要求服务时，会需要accept connection，可用以下方式 int connectclient(void) { int socksize=sizeof(hostaddr); unsigned char * addr; clientsocket = accept(daemonsocket,(struct sockaddr*)&hostaddr,&socksize); if (clientsocket?0) return 0; addr = (unsigned char *)&hostaddr.sin_addr.s_addr; printf("incoming address:%d.%d.%d.%d\n",addr[0],addr[1],addr[2],addr[3]); return 1; }

不同操作系统不同，由TCP协议定，比如 Linux 2.6.6 ：/proc/sys/net/core/rmem_max： 4194304 //4M 查看/proc/sys/net/core/wmem_max： 8388608 //8M 所以，能设置的接收缓冲区的最大值是8M，发送缓冲区的最大值是16M。